I've found that the ringed Tigres are more docile to handle while the ABC's seem to have a bit of a temper at times!

I've got experience with the X61 ABC, S61K ABC and two S90K rings, plus the S45K ABC and finally the G34 and G51 ringed engines. The Ringed engines are so smooth to operate and much easier to start. I'd not buy any of the two though, I'd go for the G-75 ring and get more power than the 61 ABC and the smooth handling of the ringed engine.