IMHO next gen consoles, whether it be the Xbox one or the ps4, are both as of right now basically useless. Note that I have an Xbox one, therefore I am speaking from experience. Everything I have it for: Gaming, browsing social media/the Internet, and using apps like Netflix, can all be done on a PC and/or a 360/ps3. The exclusive games that have come out so far don't interest me at all, and the lack of content is disheartening.
To address the topic at hand, though, I would only purchase a second copy of the same game if 1. There is a great diversification of content between games or 2. The game comes at a reduced price. Severely reduced price. Like I'm talkin $20 or less here.