Ubuntu :: Tabbing Between Pages Slows Down - Performance Being Impacted

I'd noticed the RAM-usage issue, in that at boot and without browsers running, it sits right around 50% memory usage in both desktop and laptop. Again, no problem there. What kills me is when I run Firefox and Chrome at the same time (which I often due for development reasons, and because I have various accounts set up in each). When that happens, RAM usage will push 85-90% or higher. If this were just caching I wouldn't care, but this actually causes the whole system to slow down. Tabbing between pages slows down, sometimes the whole desktop will freeze for a second or two, it can take up to 10 seconds to get the screen back from the screensaver, applications & menus are slow to respond, etc etc. Killing one of the browsers will knock RAM usage back down to 70% or so and the sluggishness stops. I could have an identical number of windows open (two browsers w/ several tabs, big GIMP image, multiple small apps in parallel).