The only PURE difference is the exams you have to sit after your ADL training. Depending on experience most new joiners sit 7-9 exams in HKG... but those coming from a pure piston background have a few extras:
Piston and Jet Engine Theory
Advanced Systems (dont know the exact title.... but Hydraulics etc)
and Electrics.
There often seem no rhyme nor reason behind CADs logic with regard to who sits what exams but, save to say, if you have less than 100hrs on any particular type CAD ignore it.
We have C130 pilots who have to sit Loading exams and Navaho pilots who get that credited.... and people from the same companies sitting completely different exams.... but the piston folk definitely sit 2-3 more.
Proably not unjustifed; quite amusing in fact to see them getting used to jet engines in ADL!
"Can it really be this simple?"
The rest, sims etc at CX is just the same for all. Lets face it the cadets have no jet time and get on just fine. I agree with Shortly.