The RA-TECH stuff will be cheaper than ordering in Cradle stuff from the states
And yea -- it' a little challenging to install if you're new to gas-blowback systems... but it's something I'd say even TheNooblord could do properly
I'll help make up your mind:
Cradle stuff you need to disassemble your bolt and place different rings on a piece to adjust your FPS
the RA-TECH you stick a small key inside the bolt and adjust the FPS by essentially turning a screw.
As for external upgrades on one of these things... Here's one I built for a buddy of mine a few months ago:
I think you should copy it