Dude - i have both and regually play on line with my mates - and if you want to use this as a yard stick go for RV6 - GRAW2 always seems to crash and the online experience is extremely poor and unreliable.
I have both and now GRAW 2 just sits in its case. I found the online play to be very poor, for some reason there was what I call screen lag. You would move the cross hairs to aim and there would be a slight delay in the response, which made it harder to aim.
The maps on GRAW are huge and I would wander around and then end of getting sniped from across the map and have to walk all the way back again.
With Rainbow Six, there are no such problems and it really is a blast to play. Smaller maps and lots of CQB fun. Try and avoid playing all the same maps over and over again. I played some really good games of assassination yesterday, probably the only game type that will give you any team work.
Probably the last GRAW title I'll buy, as I haven't been impressed with any of them.
I have GOW and Battlefield 2 but i was just looking for a slightly different experience:-
I am one of the least competative online opponent's you could hope to meet, partly because of my wholly average ability, and partly because competition is just not in my character, when i get fragged i just laugh and start again if i have a ratio of 1/10 (Kills/Deaths) i've had a stormer....lol