To answer your question in the title of your thread...
Both? LOL!
Seriously though, I think the best option (having been an FBS user for the past 7 years) is to have FBS AND Multi-IQ in your arsenal. As you note, the Safari is slow, the Equinox is anything BUT slow. FBS is deadly on deep coins, but "less good" in trash and especially iron, where the Equinox has a big advantage in iron. Deep silver is the forte of FBS, Equinox has the advantage it seems on deep mid to low conductors (while still doing very well on deep silver). One is waterproof, one is not, one is heavy, one is light...in other words, where one is a bit weak, the other is strong, and vice-versa. I really think these two technologies should be seen as very "complementary" units, one filling in whatever "holes" the other may have. I really believe that what will be borne out, long term, is that someone is better off with BOTH an FBS unit and a Multi-IQ unit in their arsenal, than they would be with either/or.
SO -- if you can keep BOTH your Safari (or an E-Trac), and ADD an Equinox, I think you will have the best of both worlds.
Steve