I use to have a snobby attitude towards Blender. But the new version is pretty usable. It works with a range of renderers. But I'm even impressed by the new internal ones. Check this out.

http://blendernews.org/xe/?mid=Feature_Articles&document_srl=1274


While the rendering may be capable, it seems there are issues importing MoI OBJ files. If you get over that hurtle the best renderer may be a free one…

As for the scale of your objects, why not cheat? If the renderer you choose can’t do small stuff scale it up.