I driven both 335i and the new M3. I pick a M3 over 335i, much sportier drive than 335i. But a 335i is much cheaper to own and maintain and offer a great performance that is more than enough for cardrivers.
If money is a problem then go with 335i, I think you will be happy with it. I dont know were you live but if Alpina B3 is for sale were you live, then take a look at it. B3 gives you 360hp (including BMW warranties) and is cheaper than a M3.