I played my first last night, thinking it would be a quick game to end the evening with. My first opponent did not show up -- it took a bit over 30 minutes to blind him out.

I would imagine that the ROI in a 4-player $5+0.25 would be less than the ROI in a 2-player $10+0.50 because your opponent in the money round will on average be tougher (having already won a HU). Probably a very small difference, but a difference none-the-less.