We put our A109S onto a 170ft Yacht regularly.
Bit tight but doable - only when moored though, way too tight to land on when under way.

It is more of a issue of finding the right yacht for the helicopter you intend to operate. Your yacht will have some design limits as to weight on the helipad , distance to tail rotor, main rotor obstructions. Pitch, Roll and Heave limits of the respected rotor system to allow takeoffs, landings. Look to port of calls, availability of parts, maintenance.

Just about every sort of helicopter has been on some boat at one time or another. Give yourself plenty of room to obstructions. Plenty of power available as in operating below HOGE weights. Either aircraft will work fine given the room to land.

Have you contacted Nigel Watson from Heliriviera? Check out that website. They're the best folks to ask about what a/c to buy and to what specs you want.

Maintained/operated an S76A+ from a 260ft yachet for a few years.