I'd go with paved, given the option. It should reduce the critter factor and the tires won't sink in. But put wooden boards or rubber mats beneath the tires. Concrete will suck the oils from the rubber in your tires and they will last longer if protected. Also, cover your tires to protect them from UV rays. And don'e forget to cover your AC roof unit to prevent ice and snow buildup. Over time, it's hard on the hardware up there.
2015 Jay Flight 32RLDS Elite
2012 Chevy 2500HD Crew Cab LTZ (6.6L Duramax/Allison)
Equalizer Hitch (1200# bars)