Sometimes you just have to wave a white flag, concede your ground and head in the opposite direction. Perhaps you could've kept on fighting, but why bother when the enemy is fierce and there are equally fertile pastures to occupy? It seems as if BMW faced such a scenario when it redesigned its Z4 roadster two years ago. Instead of futilely taking on the dynamic midengine perfection of Porsche's Boxster, BMW went in the opposite direction toward comfort, luxury and refinement.

Indeed, the latest Z4 puts a greater emphasis on these aspects more than its predecessor and many other entries in the class. It all starts with its retractable hardtop, which, like the Mercedes SLK, makes the Z4 a more versatile, all-weather choice. Inside, the 2011 BMW Z4 offers more room than its competitors, impressive rearward visibility and a luxurious, nicely styled ambience. On the road, the Z4's superb ride quality sops up bumps like a much larger, more expensive convertible along the lines of Mercedes' SL. In fact, the Z4 often feels like it belongs to that bigger, more refined class of luxury roadsters.

Of course, even if the Z4 has carved a new grand touring niche for itself, BMW is still known for building the "ultimate driving machine." For 2011, the Z4 is now available in a spicier variant, the new sDrive35is. Trust us; it's a lot cooler than its clunky name sounds, boasting 35 additional horsepower from the 35i's twin-turbo inline-6, enhanced steering and an M Sport package that adds adaptive suspension dampers, 18-inch wheels, an aerodynamic exterior kit and sport seats. That package is also available on the other Z4 models.

If you're looking to buy a luxury roadster, it all comes down to a simple question: What kind do you want? If you want a nimble convertible with an uncompromised connection between man and machine, then your answer is the 2011 Porsche Boxster. If, however, you desire a convertible that puts an emphasis on comfort, luxury and style while still keeping the drive interesting, then the answer is a little tougher. The 2011 Audi TT and 2011 Mercedes-Benz SLK fall on this side of the roadster coin as well. But in general, the 2011 BMW Z4 is a more complete package. It may have ceded its previous ground to the Boxster, but in the process, it's arguably become king of its own hill.

The 2011 BMW Z4 is a two-seat retractable-hardtop luxury roadster available in three trim levels that correspond with engine choice: sDrive30i, sDrive35i and sDrive35is.

Standard equipment on the sDrive30i includes 17-inch wheels, adjustable sport driving settings (steering, throttle and automatic transmission if applicable), automatic adaptive xenon headlights, automatic wipers, a fully powered retractable hardtop, cruise control, leatherette premium vinyl upholstery, six-way manually adjustable seats and a sound system that includes a single-CD player, auxiliary audio jack and HD radio. The sDrive35i gets you a more powerful engine, sun-reflective leather upholstery, automatic climate control and brushed aluminum interior trim.

The sDrive35is gets an even more powerful engine, a standard dual-clutch automated manual transmission, sportier steering and the M Sport package that is optional on the other Z4 trims. This package includes 18-inch wheels, adaptive suspension dampers, an aerodynamic body kit, increased top speed, a thicker M steering wheel and 10-way manually adjustable sport seats with power bolster adjustment.

A regular Sport package available on the 30i and 35i includes only the suspension, seats, increased top speed and 18-inch wheels (the 30i sticks with the 17s). The Cold Weather package adds to all models heated seats, a heated steering wheel, retractable headlight washers and a trunk pass-through. The Premium package adds auto-dimming mirrors, power-adjustable seats, BMW Assist telematics, Bluetooth and on the 30i, leather upholstery and automatic climate control. The Premium Sound package adds a 14-speaker sound system with two subwoofers, satellite radio and an iPod/USB adapter. Many of the above package items are available as stand-alone options, along with Comfort Access keyless entry (push-button start is standard), automatic transmission shift paddles, front and rear parking sensors, automatic high beams, a navigation system (includes the iDrive electronics interface) and a six-CD/DVD changer. The 35i and 35is can be equipped with 19-inch wheels.

The 2011 BMW Z4 sDrive30i is powered by a 3.0-liter inline-6 that produces 255 horsepower and 220 pound-feet of torque. A six-speed manual transmission is standard and a traditional six-speed automatic is optional. BMW estimates the 30i will go from zero to 60 mph in 5.6 seconds with the manual. EPA-estimated fuel economy with both transmissions is 18 mpg city/28 mpg highway and 22 mpg combined.

The Z4 sDrive35i gets a twin-turbocharged 3.0-liter inline-6 that produces 300 hp and 300 lb-ft of torque. A six-speed manual transmission is standard and a dual-clutch seven-speed automated manual is optional. EPA-estimated fuel economy with the manual is 18/25/20 and 17/24/20 with the automated manual. In Edmunds testing, the 35i manual went from zero to 60 in 5.2 seconds.

The Z4 sDrive35is gets a revised version of the 35i's twin-turbo engine good for 335 hp and 332 lb-ft of torque. A temporary overboost function pumps torque up to 369 lb-ft. The dual-clutch automated manual is standard. BMW estimates a 0-60 time of 4.7 seconds. Estimated fuel economy is 17/24/19.

Side impact airbags, antilock brakes with brake assist and stability control are all standard on the 2011 BMW Z4. The antilock brakes also integrate several features designed to improve braking performance, such as periodically wiping the brake rotors dry when the windshield wipers are in use and automatically snugging the pads to the rotors if the driver abruptly lifts off the throttle. BMW Assist emergency telematics is optional.

The roof is made of aluminum and incorporates a structural support system that helps protect occupants in case of a rollover accident. To provide protection in the event of a top-down rollover, there is a steel hoop behind each seat.

Even the base 2011 BMW Z4 sDrive30i is an entertaining drive thanks to its willing and exceptionally smooth 255-hp inline-6. The twin-turbocharged sDrive35i and sDrive35is are better yet, offering up authoritative yet refined acceleration. The Z4 is also characterized by its adjustable driving settings that alter steering effort, throttle response and, when optioned with the automatic transmission, shift response. Normal mode makes life a little easier around town, but the Sport and Sport+ settings are more appropriate for a roadster like the Z4.

The new M Sport package that's standard on the 35is and optional on the others should be a must-buy for serious drivers. Having said that, though, no package or adjustable settings will make the Z4 as engaging to drive as a Porsche Boxster -- the steering in particular is a bit of a letdown, providing less road feel than we'd like from a sporting car. However, we think there's a place for such a grand touring roadster and the Z4 certainly does it well.

The 2011 BMW Z4's cabin is sleek and upscale. High-quality materials abound and combine with diverse shapes to create an undeniably premium environment. Thankfully, BMW didn't forget about practicality along the way. There's a wealth of legroom in a segment not known for it, and plenty of storage space.

With a simple touch of a button (done while depressing the brake pedal), the Z4's two-piece retractable hardtop folds into the trunk in 20 seconds. With the top raised, visibility is unmatched for a roadster thanks to the Z4's large rear quarter windows that eliminate the typical convertible blind spots. The large area needed to swallow the folded roof also creates an expansive trunk (with the roof raised) capable of holding two sets of golf clubs and a carry-on suitcase. Even when the top's lowered, though, there's a deep, reasonably useful space for a pair of carry-on suitcases as well as a moderately sized pass-through that effectively expands trunk space to accommodate long items like skis or golf clubs.