The best thing to do is to go try them out in a shop. Having said that, I'm guessing that if you liked the old tab and found the 10.1 too big, you will probably prefer the 7.7 over the 8.9. The 8.9, as far as I can recall, has the same internals as the 10.1. The 7.7 is only marginally larger than the old 7, has a faster processor than all of the other galaxy tabs, and is the lightest too. And has the best screen.
Sent from my GT-P6800 using xda premium
Previously: Samsung Omnia (July-Dec 08) | HTC Touch HD (Dec 08-Dec 09) | HTC HD2, (Dec 09-Mar 12) | Samsung Galaxy Tab GT-P1000 (Mar 11-Jul 13)
Currently: Samsung Galaxy Tab 7.7 GT-P6800 (Jan 12-) | Galaxy Nexus (Mar 12-) | Nexus 10 (Sep 13-) | Nexus 5 (Nov 13-)