My understanding (not confirmed) is that Netscape is prone to use the IE engine (i.e. Active X) unless it has reason not to trust that website. That is nowhere near strict enough for me. I don't want to use IE/Active X if I can possibly avoid it. So, Firefox for me.
P.S. The recent Sony copy-protection uninstall fiasco involved SEVERE security risks with Active X. That made me even more distrustful of all that.