My experience is the reverse. I recently stopped using Chrome and switched back to Firefox 3.6 because Chrome was using over 3 gigabytes of memory with about 40 tabs open. (40 tabs sounds like a lot until you realize that no single workspace of my 10 active ones had more than 10 tabs).

With Firefox I've had over 100 tabs open simultaneously.

Love/hate with Firebug, though. I can't work without it, but it does eat a lot of memory and slow things down.