Much though I prefer the 7.7's display, if I were deciding between the two [Galaxy Tabs] today I'd buy the Tab 2 7.0 in a heartbeat. Why? It runs Android 4.0, and the jump from Honeycomb to Ice Cream Sandwich makes a world of difference. The lag and stutter you can't help but notice in Honeycomb are virtually non-existent on the Tab 2 7.0, and the whole experience of using the OS is much more pleasant. Scrolling is much improved (though still not totally seamless), and opening and closing apps is a much more reliable and quick experience. It's not perfect — rotating the screen still takes too long, and swiping between home screens can still stutter a bit — but it's oh so much better.
A number of core apps are improved in the new OS as well. The browser pinches and zooms better, and renders sites much more accurately; the Gmail app is prettier and more intuitive; even the on-screen keyboard is better. Ice Cream Sandwich finally makes Android feel like a mature tablet operating system.