Like 1586 said, your first decision is box or bulk.  Or mini-bulk bags. I have been told the mini-bulk bags are the least expensive choice for the seed company and may give a discount for using them. 

We chose the Clark box tender.  It puts 4 boxes in line and not very high off the ground.  It uses a poly cross auger and a poly fill auger.  Seed damage is at worst the same as a belt.   A belt can be very gentle, but usually they are operated so fast the seed bounces off the deflector at the end and might was well be ran through an auger.