We have approximately 8 acres and have had as many as 5 horse at one time but mostly 4, now only one (I'm getting too old, LOL!). We have an outdoor riding ring roughly 100ft by 70ft, dug down with added sand of about 10 inches, we used a landscape rake for grooming and it did really well with every other tooth removed. We have about 3.4 acres of pasture divided into 2 pastures although this seems small, and it is, we alternate the pastures every two weeks and then mow the used pasture with a 52 inch zero turn commercial mower. We also use the zero turn mower to mow our yard which is approximately 2 acres of mowing.
In 1988 we purchased a JD 650 (17hp) with front-end loader and backhoe. The 650 did everything we needed it to. We used the tractor in the beginning to mow the pastures with a 5 ft rear mounted mower, this my friend was a big PITA. The rear mower was too cumbersome and the constant hooking up and unhooking got old real quick. I soon came to the conclusion that the tractor was not the best suited for mowing at least for me. Our zero turn mower will run circles around any compact tractor when it comes to mowing.
A front-end loader is a must have, IMO. Shoveling horse manure gets old real quick also. You may want to look into a small manure spreader also. The backhoe came in handy for a lot of stuff and also came in handy when I bury a horse.
With all this said I will now say our JD 2320 tractor is the perfect tractor for our needs. Bigger is not at all always better.