Silken fluidity perfectly describes the character of the power plants, steering, and brakes on the 2006 BMW 3-Series. We sampled the new 325i Sport with a six-speed manual transmission and the 330i Sport with a Steptronic six-speed automatic transmission. At Pennsylvania’s BeaveRun raceway, we also drove a 330i Sport with a six-speed manual around the road course.

That car was our favorite. It pulled strongly and smoothly all the way to redline, it’s 18-inch Michelin run-flat tires gripped extraordinarily well, with a slight tendency toward understeer in tighter hairpin turns, and its Active Steering system, which reduces the degree to which the wheel must be turned to negotiate sharper turns such as when parking, proved its mettle in the slalom course. Even the brakes worked flawlessly, lap after lap, never hinting at fade or suffering pulsation in the pedal. Of course, it was in the mid-40s and breezy at BeaveRun, so the rotors and pads had plenty of time to cool between applications.

Our 325i Sport with a manual was quite entertaining, and returned 24 mpg during our trip to the track despite the fact that we drove it like somebody else was paying for the gas. Though the 325i now makes almost as much power as the old 330i, the redesigned 3.0-liter inline six manages just 185 lb.-ft. of torque, making it feel a bit sluggish. Gratefully, rowing gears to access the power is sheer bliss, the stick gliding from gate to gate and the clutch delightfully light and easy to engage. BMW has also added a hill-holding feature to prevent excessive clutch slipping on hills. Its 17-inch Pirelli Eufori run-flat tires were a little loud, and we detected more wind noise than expected where the windshield pillar meets the roof, but otherwise there’s little to complain about. The 325i is just as much fun to drive as the 330i, just not as fast.

Our least favorite is the car most people will buy, the 330i Sport with the Steptronic automatic. Labeling this as our least favorite 3 Series, by the way, is like saying that Chubby Hubby is our least favorite of three Ben & Jerry’s flavors. This car rode on 18-inch Bridgestone run-flat tires that were quieter than the Pirellis but provided a harsher ride, thanks to slightly lower sidewall profiles. Plus, when driving hard, the transmission sometimes delivered downshifts that came a split-second later than we wanted. We could have shifted for ourselves using the Steptronic feature, but BMW insists on using a non-intuitive tap-up for downshifts and tap-down for upshifts, so we left the selector in fully automatic mode. Nevertheless, we extracted a 20.2-mpg average from the 330i, which makes 255 horsepower and 220 lb.-ft. of torque, compared to the 325i’s 215 and 185 ratings.

No matter which 2006 3 Series we drove, the Sport suspension setup proved a gift to enthusiast drivers and a curse for luxury seekers. The car rides stiffly, and every little ripple in the road is telegraphed to the cabin. Another trait we disliked was the tendency, on undulating or heavily patched road surfaces, for the front tires of the both the 325i and the 330i to tug from side to side. Skip the Sport package if you’re likely to stay away from aggressive driving.