Sarenax, I moved your post to a new forum, but only because it wasn't really related to the product whose forum it was in originally. You didn't do anything wrong, in other words. :-)
I don't know if there's one clear winner with regards to browser security, partially because not all security risks come from within the browser. If your flash plugin is vulnerable, that can be exploited in any browser. Additionally, the answer changes over time, so the best approach may be to just keep an eye out for known security problems and be cautious in general.
This doesn't directly answer your question, but one known security problem is with the version of Java - another cross-browser technology - that Mac OS X uses.
There's an unaddressed bug that folks regard as pretty dangerous; folks are unhappy that Apple hasn't patched it yet, and are recommending that Java be disabled in all Mac OS X browsers until that bug is fixed. In OmniWeb you can disable Java in the Security pane of Preferences. I believe the same is true in Safari, as well.
Other things you can do to make yourself more secure is to be careful when clicking links in email. You can be sent an email with a link to a site that looks like your bank's website but actually isn't; it's a site that wants you to get confused and enter your PIN so they can log in on the real one.