I drove an E92 (built 2007) N54-based 335i and loved every bit of it. Fortunately I wasn't too affected by most N54 problems as I only experienced a few and warranty saved me every time.
I am driving an F32 435i Xdrive now (N55 engine) I can also say I love it! It has almost 74.000 km and except for the leaking AC condenser (replaced under warranty) I have had ZERO issues.
It's a tough choice I admit. I will simply say go and testdrive them and get your own impressions and feelings for both. And whatever you decide know that you cannot go wrong.
