Now in its third year, the 2015 Cadillac XTS is the closest thing Cadillac has to a full-size flagship sedan, at least until the top-tier CT6 arrives. It serves up a comfortable ride, standard features galore and plenty of passenger space. Granted, the XTS may seem a bit ordinary compared to true flagship models from Europe, Japan and even Korea. But with its striking looks and supreme comfort levels, there's little question that this Cadillac is determined to earn your attention.

We were pleased with last year's addition of the XTS Vsport model, which boasts a turbocharged 410-horsepower V6. Paired exclusively with all-wheel drive, it delivers serious performance along with sure-footed traction through the seasons. The real attraction of the XTS, though, is the sheer amount of space it provides. Rear seating, in particular, is quite generous, and the trunk is one of the biggest you'll find anywhere.

One of the XTS's closest competitors is the 2015 Chrysler 300, which offers a rear-wheel-drive platform, available all-wheel drive and a choice of V6 or V8 power. The redesigned 2015 Hyundai Genesis matches the Chrysler on each count, and it adds a newfound upscale character that makes it seem like a genuine bargain. On the higher end, you could look at models like the 2015 Audi A6 and 2015 Mercedes-Benz E-Class, but they're really midsize cars and don't come close to matching the Cadillac's interior room. At the end of the day, if you like the idea of a full-size luxury sedan in the classic American mold, the 2015 Cadillac XTS is bound to appeal.

The 2015 Cadillac XTS is a large luxury sedan sold in four main trim levels: base, Luxury Collection, Premium Collection and Platinum Collection. Note that the turbocharged Vsport is only offered in Premium or Platinum trim.

Standard equipment for the base XTS includes 19-inch wheels, adaptive suspension dampers with automatic leveling, xenon headlamps, LED taillamps, heated mirrors with puddle lamps, rear parking sensors, keyless entry and ignition, remote start, dual-zone automatic climate control, eight-way power front seats (with power lumbar control), a power tilt-and-telescoping multifunction wood-and-leather steering wheel, leather seating surfaces and 60/40 split-folding rear seatbacks. Standard technology features include Bluetooth phone and audio connectivity (for up to 10 devices), a new 4G LTE connection with WiFi hotspot capability, an 8-inch touchscreen that serves as the hub of Cadillac's CUE infotainment system, OnStar, voice controls and an eight-speaker Bose sound system with a CD player, satellite radio, HD radio, USB connectivity, an SD-card slot and an auxiliary input.

The XTS Luxury Collection adds visible dual-exhaust outlets in the rear fascia, illuminated door handles, rain-sensing wipers, power-folding mirrors, interior LED lighting, extended wood interior trim, a heated steering wheel, driver and front-passenger memory functions, heated and ventilated front seats, a navigation system, heated rear outboard seats, front and rear parking sensors, a rearview camera and an automated parallel-parking system (front-wheel-drive models only).

An optional Driver Awareness package for the Luxury Collection trim adds lane-departure warning, lane-keeping assist (FWD only), a blind-spot monitor, rear cross-traffic alert, forward-collision alert and a vibrating safety-alert driver seat.

The Premium Collection comes standard with the Driver Awareness package, and it adds adjustable thigh support for front passengers, automatic adaptive headlights, a head-up display, an upgraded 12.3-inch driver-configurable gauge cluster display, a 110-volt power outlet, a 14-speaker Bose surround-sound audio system and tri-zone automatic climate control.

The Vsport Premium adds 20-inch wheels, an electronic limited-slip differential and a sportier-looking grille, though it loses the automated parking system and lane-keeping assist due to its standard all-wheel-drive configuration.

An optional Driver Assist package for the Premium Collection and Vsport Premium adds adaptive cruise control and a forward collision mitigation system with automatic braking. A power rear-window sunshade and manual rear side-window sunshades are also available.

Both the Luxury and Premium Collections are eligible for a panoramic sunroof.

The Platinum Collection includes the above options as standard, adding special 20-inch wheels with chrome accents, unique exterior styling, a faux suede headliner, upgraded full leather upholstery, extended leather trim (including the center console, door panels and instrument-panel hood) and a deluxe rear armrest with audio and sunshade controls. The Vsport Platinum is similarly equipped, including the chrome-accented wheels, but otherwise shares the Vsport's distinctions.

The Platinum Collection models are exclusively eligible for 22-way power front seats with massage functions.

Optional on the XTS Premium and Platinum is a rear-seat Blu-ray/DVD entertainment system with dual displays, wireless headphones and a remote control.

The 2015 Cadillac XTS starts with front-wheel drive and a naturally aspirated 3.6-liter V6 engine that produces 304 hp and 264 pound-feet of torque. A six-speed automatic transmission with paddle shifters is standard. All-wheel drive is available and can be identified by the moniker "XTS4." In Edmunds testing, an XTS4 Platinum went from zero to 60 in 7.3 seconds, a second or so behind similarly priced and powered luxury sedans. EPA-estimated fuel economy stands at 21 mpg combined (18 city/28 highway) with front-wheel drive and 20 mpg combined (17 city/26 highway) with all-wheel drive.

If you want more pep, the Vsport Premium and Vsport Platinum trims come with a turbocharged version of the 3.6-liter V6 that produces 410 hp and 369 lb-ft of torque. All-wheel drive is standard with the turbo V6, as is a six-speed automatic. We clocked an XTS Vsport at 5.4 seconds from zero to 60, which is about average for a premium luxury sedan with an upgraded engine. The EPA rates the Vsport at 19 mpg combined (16 city/24 highway).

The 2015 Cadillac XTS comes standard with antilock disc brakes, stability control and traction control, front and rear-seat side airbags, side curtain airbags and front knee airbags. Also standard is OnStar, which includes automatic crash notification, on-demand roadside assistance, remote door unlocking, stolen vehicle assistance and turn-by-turn navigation.

Available safety features include adaptive cruise control, forward collision alert, a more advanced forward collision mitigation system with automatic braking, a blind-spot monitor, lane departure warning, lane-keeping assist, rear cross-traffic alert and a vibrating driver seat that alerts the driver to an impending collision.

In Edmunds brake testing, an XTS4 came to a stop from 60 mph in 123 feet, which is average for a car in this class wearing all-season tires. The XTS Vsport required a foot more.

In government crash tests, the XTS received a top five-star rating overall, with five stars for total frontal impact safety and five stars for total side crash safety. The Insurance Institute for Highway Safety gave the XTS its highest possible rating of "Good" in its moderate-overlap frontal offset impact test as well as the side-impact, roof-strength and whiplash protection (seats and head restraints) tests. The IIHS also rated the XTS's optional frontal collision warning and mitigation system as "Superior."

As imposing as the 2015 Cadillac XTS seems at the curb, it's a distinctly smaller car from behind the wheel. Thanks to the standard adaptive suspension and trusty steering, the XTS manages to shrink its big body around the driver.

Nonetheless, rival sedans are generally better bets for enthusiastic drivers. Comfort is king for big Cadillac sedans, and the XTS doesn't disappoint. The same adaptive suspension that keeps the body composed in corners provides a buttery-smooth ride on most surfaces. It's far from the floaty Cadillac land yachts of yore, but when you're rolling down the highway in an XTS, there's no doubt you're in the lap of luxury.

In the engine room, the Vsport's turbo V6 really transforms the driving experience. Not that there's anything terribly wrong with the base engine, but the standard XTS lacks the confident oomph of traditional Cadillacs. The muscular Vsport, on the other hand, feels more like an old Caddy V8 off the line. Springing for the upgraded engine is a no-brainer if power is a priority.

The Cadillac XTS gives you the kind of passenger volume you expect from a nearly 17-foot-long luxury sedan. Rear riders in particular will appreciate their ample accommodations. With 18 cubic feet of capacity, the XTS's trunk is one of the biggest on the market, but it's unusually narrow, so long items like golf bags will likely need to be creatively positioned.

Of course, we're used to Cadillacs that give us room to stretch out. The XTS's futuristic dashboard, though, is something else altogether. The optional 12.3-inch gauge cluster display is beautiful, first of all, with all manner of driver-configurable options. Then there's the CUE ("Cadillac User Experience") interface, which integrates audio, phone, optional navigation and OnStar functionality into an 8-inch touchscreen display. Those familiar with smartphone and tablet interfaces will feel at home with CUE's touchscreen, as it uses similar touch, swipe and pinch commands. But it can be distracting to use as sometimes it's slow to respond to your touch inputs.

There are also auxiliary touch-sensitive buttons beneath the touchscreen, and these, too, are a mixed bag. These buttons help control the stereo and climate systems, and they can be a challenge to use if you're trying to drive at the same time. For efficient operation, you may need to look down at the panel for a bit to see what you're pressing, which of course requires you to take your eyes off the road. As slick as this control panel looks, we're not convinced that it's practical enough for prime time.