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-Dec 10 WM6.5, Nexus HD2 Dec 10-Mar 12)
Currently: Samsung Galaxy Tab GT-P1000 (Stock Gingerbread Mar 11-Mar 12, Humberos CM9 Mar 12-) | Samsung Galaxy Tab 7.7 GT-P6800 (Stock Honeycomb Jan-July 12, Stock Ice Cream Sandwich July 12-May 13, Stock Jelly Bean May 13) | Samsung Galaxy Nexus (Mar 12-; Jellybean 4.2.2 Stock)