I flew an Ultra Sport 60 that I really put through the paces (no 3D though), and I do mean a lot of aerobatics and it had nothing but standard servos in it. A lot of people will dismiss standard servos as not being up to the task, but for a lot of people out there they will rarely need more servos than the standard servos. But..... The best way to determine is check with the aircraft manufacturer. They will normally indicate what size servos to use on any given plane.

Hope this helps

Ken