Well if you're asking about performance and not so much security, I'm currently using Firefox for most things as it's what I'm accustomed to. For me it's not slow at all though. At least not in my opinion. Although I have found that Firefox does eat up a lot of memory... I've got plenty to spare though. I've used Chrome a bit, but for the time being it's kind of buggy with Flash and Java so I haven't switched yet. Chrome does have some nice features though such as being able to drag out tabs as new windows and vice versa.