The Tile Tabs / Split Screen Layout add-ons for Firefox & Chrome respectively are okay, but it depends what you have on each tab window, depending on how well people like it. I think folks have had probs in the past with buggy Flash (initial Flash 13 was horrendous last month), or had too many other processes going on at once to give them a smooth experience.
We're all using either Firefox 28 / 29 at time of writing, or Chrome 34 and don't really overload with Add-ons (just the normal bits and pieces), but some websites (the ones with Flash) seem to prefer Firefox in general, although there's very much of a muchness between them all now.
They can all (Safari hasn't really been mentioned thus far in this thread - it's always stable though) give the same experience and it's rare we would even think of what browser we're using any more. Usually dictated by where we dumped that oft-used Bookmark we're looking for the Bookmarks Toolbar most often, more than any other criteria.
If pushed though, I'd side like the majority here with Chrome on the Mac at present (once you've a few useful add-ons initiated above the bare bones starting point). Preferences access isn't that great compared to Firefox' or Safari's layout though.
Can I also say that an Extra Monitor is also a good option for increased efficiency. Even 24" ones are dirt cheap now on Amazon Warehouse. You can pick new repackaged ones (nothing wrong with the contents) up for around £90 quid on there. All our Macs here have at least 2 monitors each, with E-mails, browser and Adobe CC app tabs etc. on one, whilst main screen handles work duties.