650 or 1000

I posted about getting a XMR but I decided not to go that route. The dealer I was approved at to buy a new 4 wheeler has a 650 and a 1000 for sale. There both demos so there gonna take more money off of em. But I do alot of trail riding and I don’t know what kind of mileage I would get with the 1000 compared to the 650. Just want to make sure I get the right wheeler.