Here's a pretty good definition of buffebloat from dslreports.com
there's also another definition on this page too:
http://callofduty-forums.com/community/threads/improve-your-online-experience-bufferbloat.47279/
Having high bufferbloat is like adding extra ms to your ping times in a sense.So you want a router with QoS and bandwidth management so you can give you system bandwidth priority, stabalize the line, and lower your bandwidth until your router isn't being flooded by packets that it has to buffer( the more packets your router has to buffer, the worse off you'll be). I think most routers with stock firmware have QoS I think, but not many let you manage your bandwidth too.( The Netduma and the router I listed are one of the few.)
B is okay, but you'll notice a difference with A. I had been playing with an F rating in terms of bufferbloat; that's like 1900+ms of extra time added to standard latency, which is insane. Now I get a constant A rating, which has made a hell of a difference.
When you're playing CoD, run the test a few times and see how your connection runs under load, if that bufferbloat rating changes to under a B, you might have big problem.
edit: There aren't to many videos relating bufferbloat to FPS's on youtube, but here's a guy talking about lowering his bandwidth ( throttling his connection down) on his Netduma router in order to solve bufferbloat, and how it improved things for him.