Opera is most secure and loads pages nicely most of the time. Downside is its closed source, so flexibility is what you can achieve by manipulating customization files, no outside tools.
Firefox is the most flexible with it's extensions and customizable files. Downside is its security and breaking of extensions.
Maxthon is fastest and easiest to use, with a decent array of plug-ins. Downside is it's an IE shell so it's weak on security like Firefox. And never any core updates to IE6. (then there is IE7)
They all have their advantages and disadvantages. I recommend having all 3 installed and dabbling with all of them on a regular basis.
I just have to blurt out that I am SO over hearing which is better, because the answer is None. It's give & take, probably always will be.
IE actually has always had the most potential to be the best all-around because it's not closed and development COULD be organized much better than Firefox is, and funding wouldn't be a problem. Problem is, Microsoft has already shown in the past how unimportant updating a browser is. After IE7 Final is out, why would this change? They just need a new hype (IE7), then they will probably leave IE out to dry like they did with version 6, with the exception of occasional security updates.