If you're referring to the spoofing of the URL in the address bar, that poses absolutely zero security threat, which is probably why it's low priority. A spoofed address (although I've never encountered it) cannot harm your system at all.
Wait... so the ability to display false information in the address bar is not a security risk?
Really?
You do realize that this hole poses a tremendous risk to user's privacy? Most people have trouble determining whether or not a site uses SSL -- do you honestly think they're gonna go about verifying that the address in the browser bar is the actual address of the page they're viewing? 'course not. To these folks, a spoofed address bar can well mean the difference between logging into PayPal and logging in to a phisher's site.
The default is to only open safe files... so it's safe.
You're joking, right? It's safe because the label says "safe files"?
Keep in mind, as far as Safari is concerned, a DMG is "safe". Unfortunately, exploits in the disk image framework mean that just mounting a DMG can compromise your system. Oops. Looks like disk images aren't so "safe" after all.
It only takes a mouse-click to turn that off, which anyone should do before using their browser. Still, it's not a threat.
I thought we were discussing default configs? If you're willing to account for post-install tweaking there shouldn't be any debate at all -- Firefox wins, hands down.
Firefox lacks a LOT of features that are only provided via add-ons.
Such as?
There are elegant and simple methods for limiting Javascript on both browsers.
AFAIK Safari has nothing like NoScript available from Apple or from any third-party dev.
Because they have more holes to patch.
So Apple is slower at patching holes because Safari has fewer holes? Assuming I go with that conclusion (which I don't, given that you've provided no evidence supporting it), I still fail to see how this justifies taking longer to patch holes. An exploit is an exploit; it doesn't matter if it's a rare occurrence -- if your users can be harmed by it you need to fix it.
The point is, the OP does not need to dump Safari for Firefox in order to have a save browsing experience. Both are good browsers. Both have vulnerabilities. Both have add-ons to provide features that aren't in the basic version. Both are safe to use on a day-to-day basis, if the user exercises some basic common sense.
Both are better than Internet Explorer. Firefox has no unpatched holes. Safari does.
Firefox allows users a simple way to control what Javascript executes and what does not. Safari does not.
Firefox (again, via NoScript) provides protection from XSS attacks. Safari does not.
Yes, both are (probably) safe for normal use, but Firefox is a slightly safer alternative.