Only two choices here? I mean, come on, there's Camino, SeaMonkey, Netscape 9 (now in beta), Opera, iCab, OmniWeb, Shiira, He-man
okay, so I made the last one up, but still, the browser world doesn't just revolve around Safari and Firefox.
After updating Safari to the 3.0 beta, again I found myself annoyed that the search engine for the search box cannot be changed without installing an add-on. I downloaded Camino 1.5 and was pleasantly surprised that although there was not a GUI for search engine management (as there is in Firefox, IIRC), there is a tutorial on adding your own that is much more helpful. For example, I was able to add a search on YouTube that sorts by date uploaded rather than whatever the default is.
I'm not much on Firefox because it has yet to become a "real" Mac browser -- kind of like Pinnochio. SeaMonkey is making great strides as it is moving towards version 2.0 -- the underlying code has been moved to use more of the same code that Firefox uses, so it has gotten some speed boosts. At the end of the day, the browser that I use the most is Camino -- it's got the right amount of polish and speed, and the developers care more about the user experience than some high-minded technological principles (although trying to make web site developers sniff for feature support rather than specific browsers is noble, it's not fair to punish Camino users because web site developers lock out browsers other than IE and Firefox when the code for Camino shares so much in common with Firefox).