I got out the sales brochure from my 2006 330 and looked this up. The sport package came with the higher top speed (brochure says 149), the sport seats, sport suspension (I think it's around .5 inches lower, but the brochure doesn't say), 18" X 8" wheels on the front, 18" X 8.5" on the rear compared to 17" X 8" for the non-sport, and a "multi-function leather wrapped 3 spoke steering wheel". If I remember correctly, the sport steering wheel is a little smaller in diameter and the rim is a little thicker than the standard wheel.
If your issue with the sport seats is that the side bolsters are too tight, make sure that you play with the adjustment for the bolsters. There's a rocker switch toward the front on the outside side of the seats that adjusts air bladders in the side bolsters. When the air bladders are cranked up to full, it is really confining in the seats. Release the air and it's just like the sport seats in the E46.
You'll like the E90 330. Compared to the E46, it's got a better ride, it's quieter, better handling, less intrusive stability/traction control and a slightly bigger back seat. It has a little more power than the E46 330 I replaced and it also gets better MPG. Overall, it's a big upgrade from the E46.