is there any difference in the front and rear diffs in a 2.5i, wrx, and sti?

if so is it a big enough difference to ever do a swap from one to another?

 

my understanding is that the 2.5 and the wrx will share a final drive, where as the sti has a different ratio. usually if your doing the swap can get a roll over with the rear diff included... if not subaru will sell you the correct ring/pinion. good luck