chris, these are a few rendering applications that I'm aware of, and what are to me their major pro's and cons.
Artlantis - (seperate application) really easy to use. comes with a material library. also, the studio version offers good animation options. reasonable quality, but not physically accurate, and has some quirks with its radiosity.
V-Ray - (plugin) very good quality. physically accurate lighting. option to light with hdri-maps. option for toon-materials. but way more complex to use.
POV-Ray - (seperate application) free. also physically reasonably accurate, but very slow if you want good quality. an exporter was made for SU6, but works with SU7 as well.
Podium - (plugin) rather cheap, very easy to use, but too few controls for my taste.
Now there are a lot more around that I haven't tried out myself, this is just what I think about the ones that I have. I must say my personal favourite is V-Ray, but Artlantis is a good second, especially when there are plants involved - because of a library that my boss has bought...
good luck choosing...