The Lexus is not a patch on the BMW. Engine is apparently crude and it does not handle. Go for a 320d or if budget is an issue a 120d is a much better car than you would think.
About 4 years ago I went out looking for a 320d (e46), I test drove an E46 320dSE a hated it. My budget would not stretch to an e90 320d so I bought a 120d. Before I bought it I thought of the 120d as a poor man's BMW but it was one of the best cars I have ever owned.
So whatever you do don't bother with the Lexus.