If my drain pipe is 1 1/2 do I stay with that for the new drain or is there any benefit or problem with using a 2" drain?

Depends on what fixture it is receiving waste from, Lav sink, bathtub or laundry tray 1 1/2", shower, washing machine or kitchen sink 2", Also depends on local codes. At times it can be just as bad to oversize as undersize.

Some new codes require. 2". Check with them.