The Core

I assume Merc has a tradition bookmarks toolbar?

Can you pick your browser agent to spoof?

Toolbar - yes and you can switch it on or off.

Browser agent - you have the choice of many different browsers: scads of Internet Exploder versions, Opera, Chrome, many device specific Safaris and a couple of fire foxes. 

>merc

I could find no significant advantages over icab, and browser agents were slightly fewer (important feature for me). It also seemed slower when loading gmail.  Overall, I was surprised how similar they've become.  Both seemed to have the same nuisances, so now I'm assuming that these problems have their basis in webkit rather than the individual browser.