Honestly, I wouldn't know how to develop anything on any otehr engine. A few years back i sat down with Sebe and tried out Torque. We realized that we would have to learn this thing for years to reach a level of similar work we have now.
A few weeks ago I instlled Unity3D and tried it. And once again, I had no clue what to do. Unity may be a great tool for programmers or whatever, but for a guy like me it is pretty much useless.
I will stay with GameStudio for the time being. I developed almost all my gymes with it and I will continue that way. Be the games good or not