Thats highly unusual to have that many fliers have that many problems with YS. I would say from what ive seen they are equally reliable but fourstrokes are perhaps more reliable to start.

At the end of the day an OS 140/160, YS 140/160 or electric will all power the modern F3A model with ease, it's purely down to personal taste.

Angus

ps the only time my YS cuts is when i tell it its allowed to