I have a Transformer Prime and I've barely used it since getting my N7. The screen resolution, CPU power and battery life of the two tablets is very similar, so apart from the metal case I'd guess a 10" Nexus would be very similar to the Transformer Prime.
Anyhow, the reason I've stopped using the Prime is because the N7 is so much easier to hold. I use the Nexus mostly for reading books, web browsing and e-mail and for all these the 10" tablet offers little except more weight. About the only think I use the Prime for now is reading comics, because on the N7 a whole page view is just too small to read.
Having said this, if the Nexus 10" had a 1080p screen I'd be seriously tempted.