FF4 had some concept where multiple tabs were tracked as thumbnails like an iTunes gallery. I'll have to find it, and I'm not sure if FF4 does it (I'll download tonight).
I like Chrome and FF always seems to have memory leaks if you keep more than 20 tabs open like I do (3-4 windows, 10-20 tabs each).
Chrome took off once they added extensions, and now it rivals FF to be honest in that regard. Plus, how nice it plays with Google services is a bonus.