It really doesn't matter as long as it works. I make alot of my models in Rhino and Amapi and export in obj format so I can uv map in UV Mapper Pro. I have also downloaded native Bryce models using Bryce textures. If it works for the scene, then use it. I prefer to explode my meshes before exporting them out of Rhino because this gives individual surfaces which makes texturing easier, sometimes when using Bryce textures on mulitsurfaces you end up with one side that refuses to texture properly. The downside is on a complicated model you have hundreds of surfaces to map and texture.