Not even BMW has been immune from the automotive industry's current trend of each model-year's successor creeping, growing or inflating nearly to the size of the next-larger class. That's why the 2013 BMW 1 Series is such a gem; at about the size of the original 3 Series, the coupe or convertible 1 Series just might be the last BMW that still upholds the nimble characteristics that once defined the entire BMW brand.

Under the hood there is more proof that the 1 Series is a genuine BMW. With the same superb set of inline-6 engines as the BMW 3 Series, the thrills are there for the taking. Transmission choices are also first-rate, with a choice of a six-speed manual, six-speed automatic or a sophisticated seven-speed dual-clutch automated manual.

While Americans are still getting used to the idea of premium-branded compact cars, there's growing support for buying small, but buying well. The 2013 BMW 1 Series might seem expensive when compared to a Hyundai Genesis Coupe or 2013 Nissan 370Z, especially if you tick each of the option packages. But if you think of the 1 Series as the only rear-wheel-drive compact from Europe, then it begins to look rather exceptional.

Still, you owe it to yourself to cross-shop a few other coupe/convertible models before making such a big decision. Consider an all-wheel-drive Audi TT, a front-drive Mini Cooper, and even flex a little American muscle with a Chevy Camaro, Dodge Challenger or Ford Mustang. Compared to any of the above, we think you'll sense the extraordinary quality and dynamism of the 1 Series.

The 2013 BMW 1 Series comes in two-door coupe or convertible body styles, both of which are available in 128i, 135i and 135is configurations.

The 128i comes equipped with 17-inch wheels, automatic headlights, foglights, rain-sensing wipers, cruise control, eight-way manual front seats, a tilt-and-telescoping steering wheel, premium vinyl upholstery, dual-zone automatic climate control and a 10-speaker sound system with a CD player, HD radio, a USB/iPod interface and an auxiliary audio jack. The 128i convertible adds different-style wheels, a fully lined power-folding soft top and a special convertible mode for the climate control.

Aside from its more powerful turbocharged engine, the 135i adds a sport-tuned suspension, 18-inch wheels, eight-way power front seats, adaptive xenon headlights, an aerodynamic kit, and (on the coupe) a sunroof. The top-tier 135is further benefits from a yet more powerful turbocharged engine, sport front seats, a sport steering wheel with paddle shifters (when ordered with an automatic transmission) and specialized exterior and interior trim.

The Premium package adds keyless ignition/entry, auto-dimming mirrors, interior ambient lighting, satellite radio, leather seating, and to the otherwise lacking 128i coupe, it further adds the 135's power front seats and a sunroof. When the 128i is ordered with the Premium package, adaptive xenon headlights with auto-leveling are available.

The 128i and 135i Cold Weather packages include a heated steering wheel and front seats. The 128i and 135i M Sport packages essentially mimic the extra features that are standard on the 135is.

Finally, the Technology packages adds to all trim levels a navigation system, BMW Apps with online information services, smartphone integration, voice commands and BMW Assist (concierge).

Unbundled, stand-alone options available on all trims include rear parking sensors, automatic high-beams, BMW Assist and a Harman Kardon surround audio system. For the 135i and 135is, BMW's variable-ratio active steering is available.

The rear-wheel-drive BMW 1 Series offers a choice of three different 3.0-liter inline-6 engines. The naturally aspirated 128i produces 230 horsepower and 200 pound-feet of torque. A six-speed manual transmission is standard and a six-speed automatic transmission is optional. In Edmunds performance testing, a manual-equipped 128i coupe sprinted from zero to 60 mph in 5.9 seconds. A convertible (300 pounds heavier), also with a manual transmission, posted a 6.7-second time. EPA-estimated fuel economy for the 128i coupe is 18 mpg city/28 mpg highway and 22 mpg combined regardless of transmission. The 128i convertible earns 18/27/21 with the automatic and 19/28/22 with the manual transmission, however.

The 135i's turbocharged inline-6 engine produces 300 hp and 300 lb-ft of torque. A six-speed manual transmission is standard and a seven-speed dual-clutch automated manual transmission (known as DCT) is optional. In our testing, a 135i coupe with the manual transmission sprinted to 60 mph from a standstill in an impressively quick 5 seconds flat and 5.5 seconds for a convertible. However, that number rose to 6.2 seconds for a 135i with DCT. EPA-estimated fuel economy is actually better than the 128i's, achieving 20 mpg city/28 mpg highway/23 mpg combined with the manual and 18/25/21 with the automated manual transmission. The manual-equipped convertible gets 19/28/22.

The new-for-2013 135is has a modified version of the 135i's engine that produces 320 hp and 317 lb-ft of torque. Though we've yet to test it, we suspect it will easily run to 60 mph in under 5 seconds when equipped with the manual transmission. The seven-speed DCT is also available.

Antilock disc brakes (with brake drying and standby feature), traction and stability control and hill-start assist for manual-equipped cars are all standard on the 2013 BMW 1 Series. Front-seat side airbags and full-length side curtain airbags are standard on the coupe; convertibles come equipped with front-seat side airbags that extend higher to protect occupants' heads. The convertible also features pop-up rollover hoops.

In Edmunds brake testing, a 128i convertible stopped from 60 mph in 115 feet. However, a 135i Coupe with the standard 18-inch wheels and summer tires came to a stop from 60 mph in an excellent 107 feet.

It'll take a real purpose-built sporting machine to outrun the 2013 BMW 1 Series on a winding road. Though some hard-core drivers might find that the car's handling isn't as rewarding as M-badged BMWs when driven enthusiastically, the vast majority of owners will find joy in the responsive steering, excellent body control and great outward visibility. The ride of the 1 Series isn't quite as refined as that of a 3 Series either, but it's quite good relative to rivals.

Even the base 128i's naturally aspirated inline-6 is a gem of an engine, sweeping from idle to redline on a smooth wave of turbine-like power. With their turbocharged inline-6 engines, the 135i and 135is crank up the power while retaining every bit of that characteristic smoothness.

The interior of the 1 Series is generally competitive with its rivals in terms of materials quality. Although there are still more hard plastics than we'd like in a BMW, the optional aluminum or wood trim dress things up a bit.

Most of the controls are straight out of the standard BMW playbook and are easy to use. The base seats are notably lacking in support given this car's performance potential, so we strongly recommend anteing up for the M Sport package and its superb, manually adjustable sport seats that some say are better than the power sport seats. The convertible's optional sun-reflective leather seating does a remarkable job of keeping your butt from roasting.

Although the subcompact BMW 1 Series is technically a four-seater, the rear seats are significantly smaller than those in the 3 Series coupe, so they're best left to cargo or those of smaller stature. The coupe's decent-sized trunk holds 13 cubic feet of luggage; in the convertible, there are 8.5 cubes left over when the top is stowed.