Oh, an old thread :)
I've used PlantStudio a lot (still do occasionally) and for me the LWO export works best, the model comes in with all the objects welded (can be split again by materials, if desired). The OBJ and 3DS export may produce files with a huge amount of  (grouped) separate objects, low-poly but difficult to handle anyway, due to the sheer amount of objects.

Lars "bigbraader"