stiff1 - what type of trail do you prefer? That may help narrow things down for you.
Mio is a a fun but short loop 27 miles. It has a good mix of everything. Not to many whoops last i rode it - some though - some sand, some hills, some rocks, some roots. fun quick loop. It then ties into the Hunt Creek loop at 35 miles. Hunt creek has a few rather bad whoop sections (which may have been groomed - the groomer was in the area not long ago) - east side (once past the whoops) has some tighter stuff, some hills. West side is much more open - fast, wider, sandy. Last I rode it - lots and lots of face slappers.
Bull Gap and Meadows - not on my favorites list - wide, quaded out stuff...fun enough i guess, but not my thing. Off top of my head dont recall milages there...but many miles of riding between the two (they tie together)
A bit further north to Atlanta (my home turf) - you have Atlanta A, B and C for a total of around 80 miles of ORV trail, plus a bunch of ORV route. C is a nice easy loop, 40 miles or so - no real bad whoop sections, scenic, ample quad width though - criss crosses off and on ORV route. A (20 mies or so) and B (20 miles or so) were both recently groomed (hey if you ride this and find a kick starter on the north west side of A loop LMK - it belongs to a buddys 525EXC!) - a few whoop sections remain on the south east side. Up the west side, some nice trail, not exactly tight, but quite enjoyable. Down the east side generally tighter than the west side (watch out for one bad mud hole a few miles north of where the B loop cut off joins the east side). Criss cross ORV route on the west side. A plus for the Atlanta trail system is that any ORV - even with NO street legal plate, IS legal on all county roads. Makes it easy to play around and explore that way.
Wolverine - 3 loops to choose from (dont have mileages off top of my head) some good stuff there...but also has some whooped out and wide stuff to. Fun trail.
I would offer to ride with you if you come this way - but I am laid up from riding for a while.