u tokin in the case of cymbals or toms? say u r comparing the same cymbal model, larger diameters giv the cymbal longer sustain and make them sound darker (but louder)
in terms of toms (comparing same model toms), naturally the larger diameter the lower it will sound, if it doesnt somethings very wrong. the more no. of plies in the shells (again comparing same material and thickness of plies), the more prjcted the tom will be