The E90 330i is a great car in its own right, and I would whole heartedly recommend it especially for the CPO warranty, but it pales in comparison to a 335i. If have your wife test drive the 330i before driving the 335i. Test drive the 330i on the freeway or open road to get a sense of how it performs over 3000 RPM. At speed, it is a fine performer, but from stoplight to stoplight it lacks the whoopee factor that the 335i possesses.

The E90 330i resale value might be a little soft because of the 335i's popularity which may work to the your advantage when negotiating a price. The CPO price of E90 330i's is typically a function of how much the dealer paid to take in the vehicle but from what I've seen the prices are fairly low compared to other CPO BMW's. And they do sell very quickly.