Oconee is very mild for wheeling, maybe some mud. The camping can be good though. Just be aware that it is open to turkey hunting right now.
Chattahoochee offers some good trails and excellent camping. We've slacked the past couple years but used to go to Chattahoochee a couple times a year for camping. Any area in particular you're considering?
Nottely River is one of our favorite campgrounds in Blairsville.
Beasley Knob is supposed to be a challenging trail if that's what you're looking for.
And I know they kind of consider Chattahoochee-Oconee as one forest but I consider Oconee the more eastern through middle Georgia part and is fun to explore but not as scenic. Good hiking but not as much on the driving and camping.