IMO its all about what you want the car for.
the RB25 is a better engine without a doubt. As the ssaying goes, u cant beat cubes, and here the 25 has hlaf a litre more capacity available to make boost at lower rpm, and better torque curves, and better power all round.
The 32 gts-t vs 33 gts-t chassis wise, id have to go with the 32. Purely becuase of the extra weight the car is carrying round. The geometry of both cars are very similar, but you can definately notice the difference in the weights from the nimble feeling the 32 gives off. Nothing hampers performance both in a straight line and round corners than additional weight and here your talking abuot 120 or more kg difference
i.e. 1280kg 32 gtst
1400kg 33 gtst
Styling, its personal preference. interior I prefer the newer feeling of the 33. exterior i prefer the 32's shape and presence. each to his own.