They are all IDENTICAL. They all come from the FlyingLocust factory in China. There is no difference other than the name.
Jumping Stilts is a generic term for all bocks, whether they be FlyingLocust, 7League, PoweriSer, etc etc
ProJump sell "ProJump Stilts", which are FlyingLocust. PoweriZer, FlyJumper, AirTrekker, SpeedJumper and JollyJumper are all FlyingLocust stilts. Hope this helps