You have to drive them, as they are very different.
CPO should take care of warranty concerns.
Before graduating from my 335i to my E90 M3, I also considered the 335is, but they don't lease as well and you're getting close to M3 territory in terms of payment.
All 3 are amazing, but again I strongly urge you to drive the M, as per my initial impressions post, it is a massive difference. For a used CPO that's in your budget, I would be very, very tempted, but only if CPO and favorable terms.
Good luck and again all are amazing vehicles...