06-07 duramax opinion

Ok so I am buying a used 2500HD 4x4 in a few weeks. I can't decide if i want to get a 06 old body style with the LLY/LBZ or the 07 new body style with the LMM. I like both body styles so i'm having a hard time chosing which one I want. Give me your opinions on which is better and why and which gets better mpg please. Also which do you think would look better lifted because I'm doing a solid axle conversion with a Dana 60 and putting 40s on it.