it all depends why you're going to buy the car. I had a '00 323ci, and it left some room for improvements. If you're the type of person who would add an intake, exhaust, etc., then why short yourself and get the 323. You should consider the 330 with 225 hp.
If this is just a nice car you're going to enjoy, save some money and get the 323. Very well built, just not the one to get if you enjoy the redline.
As bvrnblss says, it depends entirely on what you want it for! But at the end of the day there is only 23bhp in the difference and .5 of a second in 0-100.
The ONLY Hellrot Red 323 in the world, emmm except for the other few thousand dotted around the world.