I have about 80 hours on both - and the enstrom is a much nicer machine to fly. Its smoother, a little faster and has a little more power. The Rrpm doesnt fluctuate as much when practicing autos and its has a better safety record.
If you have only flown a robo before though - you may find using the throttle more a bit confusing because there is no governor on the enstrom.
The enstrom is also aerobatic (no teetering head)
Still, although i do appreciate the plus sides of the robo (and yes it has a couple) - i was glad that i learnt to fly in the enstrom simply because of the throttle manipulations you have to use, and the governor failures i have had in the robo.
Hope this helps!!!
