I went through this same process 18 months ago. Found the 270 EX II very limiting in power and because of no rotation. Bought a 430 ex II for very little more and don't find it awkward at all. Of course it is taller and two batteries heavier, but, really, for the extra power, the rotating head, and the AF assist beams (which I like better than the strobe method), well worth it.
Intimidating? Ok, the 270 has a lower profile and does look kind of cool, but I don't think the 430 adds much intimidation to a 5D3 with a 24-70mm or any other lens that has a filter diameter of 77mm or so. People see that lens and that body--the Speedlite is just part of the contraption in most eyes, in my opinion.
I used to be so self-conscious I wouldn't even carry a tripod when I needed one. Heck, a 430 is practically stealthy. But, if keeping the flash comfortably in a coat pocket is a important, the 270 is better than nothing.
Convenient in a pinch? Yes. The one you use the most? From my experience and that of other Canon fanatic friends of mine, not likely.