We have a 47. There are several of them in the area. It will hold 450 bu without extensions. We fabbed 11" extensions for it and it holds right at 500 bu, a little more if you stuff it, a little less f you have to cart it out a long distance on rough field roads. It has a 12" side auger. That's really it's main drawback. Oh, and the sump design makes it to where it doesn't really clean out completely every load. A 500 is a newer cart. With the front auger it should be pretty nice. I know of a couple of F700's around that guys seem to get along with. The company is out of business so parts are a fab job.  They are a pretty good old well balanced cart.

 Here's a couple pics of our 47.  The white part is the extensions.