The greatest difference is ROTJ stormtrooper buckets and armour due to mold degradation and tweaking/re-design of the armour's edges etc.
ESB, ANH and even R1 as seeon on screen had relatively minor differences the casual observer would miss.
There are only a couple of features on the Fett helmets that jump out at me (visor width and helmet flare).
I now see more Vader mask differences than ever before but still not on the level of some fans. So my obsessive attention to detail isn't evenly distributed or I'd probably never leave the house.