Difference between E53 and E70?

[brandydan]

Hi everyone - soon-to-be-newbie here:

We have been taking our time looking for our replacement for our overworked and now living (hopefully) a quiet life 1998 323is, and have decided to go for an X5 rather than an X3 simply because with the seats down, we can fit our three dogs in the back of an X5 and not an X3 (I think that the salesperson at the local dealership almost had a coronary, though we did clean the back of all doghairs and smell ).

We are still wavering between a 3.0, 4.4 and I have even seen some decent-priced 4.8, and was wondering what the differences are between the E70 and E53? I can't get an answer from searches on this site, and was wondering if it a simple 'duh' question, as perhaps one is standard and the other is automatic, or is the size of the engine?

Thanks.