If you decide on the 7", I recommend the Nexus 7 over the GTAB2. I have and like both but the N7 is a better overall tablet and a better value as well. The GTAB2 does have a microSD card slot that allows you to add an additional 32G of storage but the N7 has a faster processor and better screen resolution. There are rumors that Google will announce a 32G model of the N7 on the 29th of Oct.
The Nexus 7 is the best 7" tablet money can buy at the moment. There is absolutely no reason to buy the 7" Galaxy Tab 2.
If you want a 10" Android tablet (I wouldn't really go down that route since they're all pretty poor) then the Transformer line from Asus is a better choice.
I prefer 7" over 10" tablets. Personally, the 10" ones are too heavy and cumbersome to use for extended periods of time without putting it down. I can hold my Nexus 7 and use it for hours without feeling strained.