I've played both machines, and my choice would be Deadpool. I know some may disagree, but it fits the theme of your business a bit better than Iron Maiden. I think both games will have staying power -- IM is obviously the more complete game right now, but it's a difficult game to master. DP is a little more accessible to casual players as the codes stand now, IMO. Also (and not for nothing), there are three other businesses with an IM on location in the area and no one has a DP as yet. I know I've traveled to a specific location just to try a specific machine -- I'm not saying that's normal (it isn't), but it's another factor to consider.
I really need to get up to Grass Valley