The long nose 50/1.8 handles much better than the "pan-cake" models. That alone is sufficient to prefer it over the other versions. Its bokeh, whilst not sterling silky, tends to be smoother than the 50/2, which on the other hand is at least as sharp.
The basic message is that one cannot really go wrong with either of these 50 normals. They all have their quirks which must be learnt in order to master the lens to perfection, but basically they deliver good, sharp images all day as long as the photographer can deal with this focal length and angle of view.