I greatly prefer left-to-right targeting. Maybe it's because I played FFXI for years with just a keyboard, but it makes just as much sense to go that way as closest-to-furthest, but with the added benefit of me being able to adjust my starting point just by rotating the camera a little.

I place myself directly to the left of what I want to target, and then it's the first I get to, even if it's three or four mobs away. It takes a split-second to set up, and there is nothing equivalently quick when targeting is done by distance.