Do you only want music or want to watch videos as well? The Nexus 7 wins there for videos.
The display size makes a world of difference when you use the device for typing/messaging. Nexus 7 wins here.
You need to be more specific about what you want to do with the device for more feedback.
I am looking into buying either the iPod touch 32GB 5th-generation or the Nexus 7 16GB.
Capacity is not a concern for me... 16GB and 32GB will both serve me well.
Which would be the better product? In terms of performance, responsiveness, capabilities, fun-ness, etc...