Well. I've 4 weeks used Linux Mint 7 (Gloria) in my one my partition, the other is Ubuntu Hardy Heron. Perhaps i'm wrong but after updated Firefox 3.0.11 to 3.5 i've tested it in Mint and Ubuntu and got much better results in Ubuntu than in Mint.
Here are some of these:
Peacekeeper: FF 3.5 ---> Mint, 990 pts, Ubuntu 1170 pts
SunSpider : Ff 3.5 ---> Mint 3550 ms, Ubuntu 2780 ms
It took these results by testing browsers three times in each Os as an average. I made it again this morning - and got the same results, FF 3.5 got better results in Ubunta than in Mint.
Also with Firefox 3.0.11 the Ubuntu partition gave better results both in Peacekeeper benchmark and in SunSpired. Further info : i've Compiz enable in Ubuntu, but not in Mint. There are also Nvidia drivers installed both in Ubuntu and Mint. More applications installed in Ubuntu than in Mint. Can anybody explain why those differences?