I agree with Armed_Blade. But if I had to choose, it would be firefox because it has a better shield against viruses than internet explorer. It's also faster and has more customization which i like
You can't go wrong with either of those in the top four. Firefox, Chrome, and Opera are all stable, secure, and fast web browsers. Firefox just has more extensions and is more customizable than the others - which is why I use it as my main web browser. But as for IE, it isn't that stable nor secure, so I rarely use it. Only time I'll use IE is to test something in that web browser or if the others aren't functioning, but that never happens.
I used to like firefox for customization, but doesn't that slow down the browsers capability?
I don't know for sure, I've never experienced speed problems with Firefox when I customize things/add things. If you add a lot of things onto the browser it'll probably slow down a little, but I'm sure that'll happen to all of them.