Geez HM, you making the boy work aren't you?
In essence the rules are the same but the parameters are different.
A separate rating is required for each type of helicopter (we don't have "classes" of helicopter as such) and 2 hours per annum must be flown on each type.
In addition, a Licence Proficiency Check must be passed for each type (with the exception of some single engine piston helicopters - if you want that level of details, then look at LASORS!).
Cheers
Whirls