Personally, I wouldn't touch the 8800GTS cards.
I wouldn't pay £165 for a 9800GTX+ either, a Gigabyte one sells for £139.
In terms of % gain per buck, that kinda went out the window when the first 8800 card came out. Since then we've all been using baby-steps, but paying daddy money.
Simple answer, neither, get a cheaper 9800GTX+, if that's the choice of 2, and order some take-away with the change
(or more seriously, more memory)