I think for pure gaming its worth the trade as my gpu is weaker than his by a good chunk and even though his isnt dx11 mine is too weak to run much dx11 settings anyway. also games are more gpu dependant now than they ever were.
The part where i come to question is on the CPU.
Most games still prefer a high-clocked dual core to a slower quad core and even after having half the cores the dual comes out just a smidge slower than the quad as far as raw computational power goes.
If you look at this chart here (http://www.notebookcheck.net/Mobile-Processors-Benchmar...) the quad core comes out at 102 where the dual core is 115
Think its worth the trade? both are in good condition as well.
If those scores are per core performance i'd say it's a fair trade off. the gpu matters most and although it may be a little rough on cpu intensive games like starcraft, total war games, skyrim, ect you should have no problem with most other games.
The 260m is the better card at higher detail settings. At lower settings they run about the same when cpu matter most.
the laptop i have is a 1366x768 display where as this one is a 1600x900 so i get more pixels to run on and that should make the gpu matter a bit more also increase overall detail.
also yes i did compare gpus on notebookcheck and the 260m is faster than the 6650m by a good chunk but isnt dx11 although the 6650m isnt really powerful enough for dx11 details anyway
the gtx 260m is better but I probably would't make the swap 6650m. You have a newer quad core cpu and it is lighter laptop.
that model (the g72 bestbuy model) laptop in particular is know for heat issues. plus it is clunkier than your acer. also with that laptop due to it being a best buy model. You are limited to dual core cpu upgrades. You cannot put a quad core in it.
I currently own the g51 rx05 model of that lappy, It runs hot and that is after extensive cooling modification.
do a test run trade, if you like the performance of the g72 then keep it.
EDIT. also the battery life of the 260 model is pretty horrible (like 1 hour on power saver), that probably doesnt matter too much but considering it is a gaming lappy but its noteworthy.