After 100 hours and 600 glider tows, I'll vote for the Pawnee. Once you get used to the strange attitude over the nose, on the ground, it's easy to fly. However it is not easy to land consistently but is very forgiving and strong - it's an agricultural implement!
Citabrias/Scouts and Super Cubs are relatively easy but they teach you not to relax on the ground. I found the Stearman fairly docile but I did not fly it in any appreciable cross wind.
The Chipmunk was much more demanding but I never ground looped one. I did not like the Auster with heel brakes.
I've not landed one yet, but I've been a passenger in a Christen Eagle II. I would say that is very demanding on the ground,