game of the year edition comes with unique skins that you can only get from there. And stuff for Blizzards other games, if you play the other games, I would.
I honestly don't find any of the GOTY/Origins edition skins super attractive. I was fine just paying $40 for my base game. Really not worth the extra $20.
Interesting tip, if you buy the base game now you can play around until black friday and then get the origins/GotY edition for only $10 more instead of the regular $20. Or you can wait and get the whole thing half off instead of just the upgrade.