Gee now that's a surprise... the Bota guys actually thought they had the better engine... imagine that, /forums/images/graemlins/smirk.gif
I think both are good machines (another surprise since I own 1 of them) but as stated it's not a direct comparison in each brands model line. The 4310 is a better equipped model, but used... if the hours don't bother you I think you could probably negotiate the price to where you want to be - otherwise brand new Bota sounds like a great plan as well. If the 7800 has everything you need, new is hard to beat, especially with interest rates as low as they are (if you finance).
I used to sell cars - I think the equation for you to answer is do I want a used tractor - any idea why such a low hour machine made it's way back? Ever heard the saying "Nobody ever sells a car because they loved it"?
Aside from that caveat, see what tractor fits your needs best, and what dealer suits you best.
Good Luck - it'll be fun getting either one! /forums/images/graemlins/laugh.gif