being honest there is no such thing as 'best'
each has their own slight differences and what suits you may not suit me and joe bloggs over there will likely have a different opinion again. Thats what makes us so interesting as a race.
My personal preference is Opera. I like it for a number of features that other often copy later.
e.g. The Voice feature is really good for me at work for example. I can open a tech site in a tab, shade the text and click "Speak" and it reads it out to me whilst I get on with other stuff. another feature I like is that each website has s set of preferences so I can easily set sites to allow pop ups on some and not on others. I like the latest versions way of showing the tabs as thumbnails of the actual web page. I like the auto sync of bokmarks and browsing history across all teh PCs/mobiles I use. I go to a website whilst at work its automagically in my history at home and vice versa.
As I said, Opera works how 'my' brain works so is best for me. You may find Firefox or Chrome or IE suits you best. The only thing with IE is all these security holes that appear.
teh best thing is to try one for a week or so and see how you get on, then try another and so on. when you feel at 'home' you've found teh one for you.