If you know what you are doing you get good results with whatever renderer you choose.
If however you dont know what you are doing no renderer will save you. Altough honestly slapping fg or a ambient occlusion on top of anything seems to help a bit.
And the maya default renderer isnt bad.. at all. Not even close. A little slow maybe, but it does require you to know what you are doing. Same also applies to prman (altough its easy to crank up the quality and get beutifuly aad objects with it, but enable raytracing and youll die standing)!