gelatine powder provide higher gelling strength
gelatine sheet need to count by weight, it has 3 kinds of gelatine - 2.5g/pc, 3.3g/pc and 5g/pc, better weight it.
tips: you can reduce half of gelatine for mousse cup, better result in texture (smooth and creamy)
of course, gelatine sheet provide much higher quality to your product.