In the grand scheme of things, who cars about a browser?
Some are marginally faster at a/b/c, but the same one slower at x/y/z. They'll all have some security bugs, so you're going to have to keep checking for updates to them all (and frankly, who cares if it gets upgraded once, twice or 50 times a year - they all do it automatically).
The only people this matters too are the ones making the browsers, the rest of us install whatever pedastole we want to stand on (wether its an Opera one, a Mozilla one or a MS one) but at the end of the day; we all have to update, patch and upgrade regardless of whatever path we pick.
As for speed ... it makes no difference. In the real world, websites dont use 9000 JScripts or whatever, so a marginal saving (in time terms) is meaningless anyway.
You get a site that loads in 10 sec on one browser and 5 on another, its doomed anyway; as there will always be a split between browsers - so you immediately alinate whatever % are using that browser. By the time sites are upgraded to what is the latest and greatest website toy, the browsers will be capable anyway.
The web runs on the lowest common denominator of the major browsers, not whichever is the fastest. So if your interested in saving 0.25sec of your life, the browser speed choice is relevent. For the rest of the human race its about wether you want to customise it, disable scripts or whatever your personal quirk is.