Comparison between Blender Cycles, Mistuba and LuxRender
With the number of external render engines available for Blender these days, it may become really hard for new artists to pick just one. I still remember the days when we had just a few options, like YafRay. The best way to get to know those renders is to try them with your workflow. Along with the practice we can always read other artists options and tests with those renders. This is why I really like articles like the one posted by bartoszstyperek with a comparison between Blender Cycles, Mitsuba and LuxRender.
The object rendered with all three renders was a car, and the results are quite interesting. If you are still trying to find the best render for your projects, it is a nice starting point to read the article. Just a quick note, this is round two of an article written by the same artist back in 2011.