I have a Rapid mk1 (new model with mk4 trigger) in .20 and been to Phild to put one of his regs on and other bits. It shoots amazling well and what a class rifle, close on 200 shots out of of the 280cc bottle
I also have a HW100 carbine with a A+M custom cylinder, this also shoots spot on and i get close on 100 shots out of it in .177
Tough call which i would choose but if i could have a HW100 in .20 would be the best pick for me
You won't go far wrong with which ever you go with, go and shoulder both and see which suits you the best