main differences is they totally different bodyshell.

engine and transmission is to all intents and purposes the same.

as is suspension and brakes, tho 33 brakes are a little better.

r32 ecu is live mappable by stu, so dont need fancy aftermarket ECU.

r32 is a good 100kg lighter.

r32 can be made 100% RWD with a simple fuse removal.

r32s and r33s can have a variable torque split controllers fitted to alter the power bias between front and rear, only cost about 150quid and makes it easy to alter handling to how you like it, doesnt make it 100% RWD tho.