1 1/2 or 2 inch PVC rough in for Bathtub and sink?

[I Hate Making Names]

I am replacing my rusted out steel drain pipes in a bathroom remodel and I am wondering if I need to and or should go from the current 1 1/2 pipe to a 2 inch pipe on either or the bathtub and the sink. Since it’s just one bathroom I’m changing the toilet to 3 inches.

Is there a reason to do one size over another?