The 2015 Infiniti Q50 is a tale of two cars. The Q50 is one of the most highly rated midsized luxury sedans by Edmunds. It also received one of the lowest grades. Wait, what?

Let us explain. The Q50S with a conventional, gasoline-powered 3.7-liter V6 received straight-"A" grades for its athleticism as well as for its good manners in everyday driving. In stark contrast to that, we gave the Q50S Hybrid a grade of "D" in the same categories. This led us to conclude: "The Q50 S Hybrid is an agreeable midsize luxury sedan ruined by a poorly executed hybrid drivetrain."

Both Q50 models feature a well-built interior with plenty of high-tech options and organic styling that sets it apart from other midsize luxury sedans. The differences between the two lie mostly in how they drive. In particular, the Q50 Hybrid suffers from uneven and inconsistent acceleration and braking. The optional Direct Adaptive Steering (also available on the non-hybrid Q50) removes the physical link between the steering wheel and front wheels and substitutes an electronic system. The result is an unsettling response delay and lack of feedback. The Hybrid also gets points deducted for its smaller trunk and rough ride quality.

With those differences in mind, we wholeheartedly recommend the standard Q50 and caution against the Q50 Hybrid. Likewise, we don't recommend the Direct Adaptive Steering, which unfortunately comes bundled with the Deluxe Touring package and may be required for some of the high-end safety technology features.

To the Q50's detriment, its rivals don't suffer from this level of duality. For this and the aforementioned reasons, we suggest checking out the Infiniti's substantial competition before committing. Of these competitors, we give top recommendations to the Audi A4, BMW 3 Series, Mercedes-Benz C-Class and, to a lesser degree, the Acura TLX. Depending on the model and options you choose for a 2015 Infiniti Q50, you either can do far, far better or rest easier knowing you made a smart choice.

The 2015 Infiniti Q50 is a five passenger midsize luxury sport sedan that is offered in base, Premium, Q50S and Hybrid trim levels. All-wheel drive (AWD) is also available for each trim.

Standard features for the base Q50 include 17-inch alloy wheels, automatic LED headlights, LED foglights, heated mirrors, keyless ignition and entry, cruise control, dual-zone automatic climate control, leatherette (premium vinyl) upholstery, eight-way power front seats, a leather-wrapped tilt-and-telescoping steering wheel, a rearview camera, twin touchscreen displays, Infiniti's InTouch infotainment system, voice controls, Bluetooth connectivity and a six-speaker sound system with a CD player, two USB ports, an iPod interface, an auxiliary audio jack, satellite radio and HD radio. The Q50 AWD includes a heated steering wheel.

The Q50 Premium adds a sunroof, heated front seats, an auto-dimming rearview mirror and a 14-speaker Bose surround-sound audio system.

The Q50S includes all of the Premium items along with 19-inch wheels, summer performance tires, more aggressive exterior styling, upgraded brakes, a sport-tuned suspension, paddle shifters and leather sport seats with power lumbar, power side bolster adjustments and manual thigh extension. The Q50S AWD adds the heated steering wheel and all-season tires.

The Q50 Hybrid Premium includes all of the Q50 Premium features and adds a drive-by-wire steering system, cabin noise suppression systems, power steering wheel adjustments, a sport-tuned suspension, leather upholstery, power lumbar adjustments for the driver and a rear-seat center pass-through to the trunk. The added features for the Q50S Hybrid and AWD models mirror the standard Q50S list.

Some features on higher trims are available on supporting models as options. The option packages listed below require the selection of the preceding package. The Navigation package adds in a navigation system and Infiniti Connection emergency telematics. Stepping up to the Deluxe Touring package gets you power steering wheel adjustments, a drive-by-wire steering system with adjustable effort, auto-dimming outside mirrors, driver seat memory functions, wood interior trim, 60/40-split-folding rear seats, a multiview camera system, front and rear parking sensors and automatic wipers. Then there's the Technology package with adaptive headlights, automatic high-beam headlight control, adaptive cruise control, front and rear collision warning intervention systems, a blind-spot warning and prevention system, a lane departure warning and lane-keeping assist system, an interior air purifier and a reactive gas pedal that can help minimize wasteful driving.

The stand-alone Performance Wheel package adds special 19-inch wheels, non-run-flat summer tires and a spare tire to the rear-wheel-drive Q50S.

Powering the 2015 Infiniti Q50 is a 3.7-liter V6 that produces 328 horsepower and 269 pound-feet of torque. A seven-speed automatic is the only transmission offered. Rear-wheel drive is standard and all-wheel drive is optional. In Edmunds testing, a rear-wheel-drive Q50 Premium accelerated to 60 mph in a quick 5.5 seconds. The EPA estimates this model can achieve 23 mpg in combined driving (20 city/29 highway). The AWD model is estimated at 22 mpg combined (19/27). A rear-drive Q50S averaged 25 mpg on our Edmunds mixed-driving evaluation route.

The Q50 Hybrid gets its power from a 3.5-liter V6 that is paired with an electric motor fed by a lithium-ion battery pack. Combined power output is 360 hp, which in Edmunds testing allowed it to reach 60 mph in only 5.3 seconds. The EPA estimates fuel economy at 31 mpg combined (29/36) for the rear-wheel-drive model and 30 mpg combined (28/35) for the AWD. A rear-drive Q50 Hybrid averaged 31 mpg on the Edmunds evaluation route.

Standard safety features on all 2015 Infiniti Q50 models include antilock brakes, stability and traction control, front side airbags, full-length side curtain airbags, a rearview camera and the Infiniti Connection telematics service with roadside assistance, automatic collision notification, stolen vehicle reporting and remote door unlocking.

Available safety features include a multiview parking camera system, front and rear parking sensors, adaptive cruise control, blind-spot/lane departure warning and prevention, and forward/back-up collision warning systems (which can scan two cars ahead in traffic and automatically apply the brakes if a collision is deemed imminent). There's also Active Lane Control, which can sense changing road surfaces or crosswinds and automatically add minor steering corrections, thus reducing driver effort and fatigue.

In Edmunds brake testing, a Q50 Premium came to a stop from 60 mph in 123 feet, which is about average for cars in this class with all-season tires. With the Performance Wheel package's non-run-flat summer tires, that distance is reduced to 110 feet. A Q50 Hybrid Sport with its run-flat summer tires required 117 feet, which is longer than average for a sport sedan with summer performance tires.

In government crash tests, the Q50 received a top five-star rating (out of a possible five) for overall crash protection, with five stars for total frontal impact safety and four stars for side-impact safety. In testing by the Insurance Institute for Highway Safety, the Q50 was awarded the highest score of "Good" for moderate-overlap frontal-offset impacts and a second-best "Acceptable" for the small-overlap frontal-offset impact test. It earned a "Good" rating for side-impact, roof-strength and whiplash protection (seats and head restraints) tests. It also earned a "Superior" rating for the performance of its optional frontal crash mitigation technology.

The differences between the conventionally powered Q50 and the Q50 Hybrid are significant. The standard 3.7-liter V6 delivers smooth and decisive acceleration, making it a standout in its class. The Hybrid is slightly quicker in testing, but in daily driving the drivetrain is prone to unsettling and unpredictable stumbles and lurches. Braking is also divergent, with the gas-only Q50 benefitting from consistent and confident results, while the Hybrid suffers from a noticeable lack of smoothness and stability. In our test track panic stops, the Hybrid's pedal would sometimes go all the way to the floor. The ride quality also suffered with the Hybrid model, with an unusual and objectionable harshness. The Q50S, on the other hand, is firm, but still compliant.

In terms of handling and steering, the Q50S receives high marks for its quick responses, composed ride and predictable nature. With the Direct Adaptive Steering (drive-by-wire) option, the physical link between driver and front wheels is removed and replaced by an electronic system with unfortunate results. It feels artificial, lacks feedback and even worse, suffers from a slight delay with quick steering inputs. It leaves drivers feeling disconnected and unsure of how the car might react.

There's plenty to like inside the 2015 Infiniti Q50, but there are also a few items to be cautiously aware of at the same time. The interior features fine materials that compare favorably against other luxury cars in this class and there's enough visual interest to keep it looking fresh. The standard seats can be overly firm, and taller passengers may desire more thigh support. The sport seats remedy these issues with more supportive bolstering and adjustments. Rear seats are roomy enough for taller adults in terms of head- and legroom.

Dominating the dashboard are two central touchscreens that control most systems. The two different displays -- one inset with an anti-reflective coating and the other mounted flush and glossy -- do look a little awkward together. Operation is also unintuitive, at least in the beginning, as users have to figure out which screen does what and both are prone to washing out in direct sunlight.

Interior pockets, bins and cupholders are adequately sized to stow your personal effects, but they're not as generous as those of a few rivals. Trunk volume for the standard Q50 measures 13.5 cubic feet, which is decent among midsize luxury sedans, but the Q50 Hybrid model's hybrid battery pack reduces that space to 9.4 cubic feet.