Basically it's semantic. 'Mesh' implies it's already been triangulated, 'editable poly' gives you the same low-level access but the faces can be quads (or, in theory, even higher-order polygons). Gotta watch that meshsmooth, too, if you're building for game applications. IMHO the main reason for the enduring popularity of box modeling is that's usually how the low-poly game figures are made, and that's where most of the $$ is to be made.