Do I need to play undead nightmare with RDR?

[Zappykins]

Hmm, I got the game of the year edition, as it wasn't much more. But have only played the regular version so far. You want to play that one first - and it alludes to the what happens in Nightmare. I started it, but it's a bit of a spoiler.

If you get the GOTY edition, it does give you access to a better horse, which is only in the DLC. Also, it depends how much you like Zombies. There is plenty of game to play in the regular Red Dead Redemption.

I'm curious about how others answer too!