I almost didn't reply, since I've weighed in on this kind of comparo before. But I have a few minutes so what the hey. From the Dept of the Completely Predicatable....
Value is in the eye of the beholder. If what you value is features, benign handling and neat gadgets, you can't really beat the TL. If what you value is driving dynamics, technical innovation and bank vault solidity, the BMW wins hands down.
The TL has several things on it's side; most of which looks better in a brochure. It is slight larger, comes better equipped for the same money and makes all of 3 more horsepower under the new SAE horsepower standard.
Let's look at each area:
Engine and Powertrain - 258 (TL) vs. 255 (330i). I'd call it a draw. The TL has a slightly beefier torque curve (230 vs. 220 ft lbs). The 330i's magnesium crankcase makes the engine much lighter. Advantage: Tie
Chassis and body - Both cars have stiff unit bodies. The BMW has lightweight alumium control arms, while the Acura mades due with steel. However, the TL can boast a front double-wishbone layout, while the BMW makes due with a simpler strut type front suspension. It seems a wash on paper. Both cars weight within 100 lbs. of each other, but the BMW simply handles better (read later in the post to find out why). Advantage: BMW
Braking - The BMW sports massive 13 inch front rotors vs. the Acura's 11.8 inch rotors. Moreover, the BMW is shod with 225 mm front tires while supporting 50% of the car's weight, while the Acura wears 235 mm width while supporting 60% of the car's weight. Even the TL's optional Brembo brakes are only 12.2 inches in diameter. Advantage: BMW
Interior/Exterior - Design is highly subjective, so again it's really whatever moves you. I personally think the TL's exterior styling is bland, but the interior is nicer than the BMW's. Advantage: Tie
Options and Features - This is where the TL runs away from the 330i. The car is feature complete at $35,000, which is the base price of the 330i. Load up the BMW to the same spec and you're talking $43,000. The cost savings in the TL is undeniable. Advantage: TL by a landslide.
So on paper, the TL is certainly a better value than the 330i. Until you start the engine and head down the road.
From my point of view, the BMW offers way more than just RWD. It's all the benefits that comes with the layout that actually matters. We'll start with accurate, linear, natural steering that's full of feedback. Then there's balance and poise at the limit which can only come from 50/50 weight distribution. And seperate from the layout, but intergral to the way BMW develops the chassis is that perfect compromise between ride and handling.
The BMW will connect you to the driving experience in a way the TL will not. Add mid-corner throttle on a car like the TL and you'll swing wide of the line while the steering wheel not only losses sensitivity but accuracy as well. Do the same in a balanced RWD car and you can control the attitude of the nose with the throttle. This is a night and day difference in driving experience. And no spec sheet can illustrate that.
The bottom for me? If you drive both cars back to back and don't feel or appreciate what the BMW does on a driving enjoyment level, save yourself 5-10k and go with the TL.
M
Having driven my parents' Oldsmobile Cutlass Supreme in the winter two years ago (
), and then my own car last winter (
), I definitely know which drivetrain I would trust in an emergency situation...
(@Swift: I would argue, though, that for an enthusiast's car, the 330i is very practical as well... 
