Well it is an iOS forum, so biased answers must be acceptable... So here goes :
The nexus 7 has good specs, screen, and that's about it for me. It has a nice look to it, good hardware, but it does lack the good funcionality an apple product has just based on the performance and ease of access.
I would go for the nexus 7 in gaming because of the ipod 4 lack of games compatible with it now, and for the future. So the nexus 7 wins, but you have to keep in mind I believe the iPod touch 4 deserves the award for functionality, just not gaming.
What are some titles you are looking to play?