There are too many variables to make general rules except:

Heavier pellet needs heavier piston to work well.
Efective piston weight is piston weight plus a third of the spring weight. A compressed coil at the spring guide end adds no weight but one at the top hat end adds all its weight (it acts like iit is part of the piston/top hat).
Heavier pistons and pellets can get away with smaller transer ports.
Heavier pistons mean more power but also more recoil.