I'm not happy with Firefox, either. It's got memory leaks. I usually have a dozen windows open with a few tabs in each, and after a week or so Firefox is taking up 700 MB of virtual space, 200MB of real memory, ridiculous. I use Seamonkey on my desktop, and Konqueror on my 500 MHz 192 MB laptop. They're bloated, too, but not as badly as Firefox, and there are just too many sites where Dillo isn't usable these days.
But one second to close a tab? Something's not right there. Perhaps your PCLinuxOS didn't make and activate a swap partition and the system is thrashing? Swap files blow, you want swap on its own partition. Can you reproduce the problem with top(1) running in a terminal? It would be interesting to see where that time is going.
Opera is a fine product. If I had to trust a closed browser, that would be the one for sure.
The beta version of a new PCLinuxOS is out and after trying Firefox I was not happy with it's sluggish performance. It would take close to 1 full second to close an open tab.
I ran the Synaptic tool, installed Opera and while I may have not found how to bookmark a group of tabs easily Opera is far speedier than Firefox.
Looks like a winning combo.