Batman is by far the better game. Not talking about playfield layout but gotg lacks a lot of gameplay at the moment and will probably become regarding gameplay the sister of aerosmith at max.
So:
Custom voice by the original actors, full access to all material, stacking possibilities, original rules (b66) vs dubbed movie scenes that are not connected to the shots you made and very straight forward rules (gotg)... easy choice for me
I strongly doubt it but with Lonnie in the lead you should not expect gotg to become a deep game like metallica, the walking dead, batman, ..
Is that a bad thing? No not all, guardians will be a more simple fun game to play, perfect for bars, ... nothing more, nothing less