I would agree with the Schweizer 300.
I started rotorcraft training almost 20 years ago on the R22, but never felt comfortable. So switched to the Hughes 300 (as they were called then). Got about 25hrs in it before I ran out of money. Never took my license, but recently did a few hours here in California to see if I still could remember how they flew (I could barely hover..
. Great fun, and I'll get my rating at some point.
The 300 looks flimsy, but it's actually built like a tank when you get close to it. Lots of cast aluminium bracing, oleo shocked landing gears and sturdy stuff. They can take some abuse. They're slow and noisy, but they're very controllable and fly well. Good training platform with good autorotational capabilities. The fully articulated head as compared to the R22's semi-rigid makes for a better training platform most instructors would agree on, I think.