depends on which version of poser you're modelling for. Poser4 wants to make everything roundy and smooth, P6 allows you to decide what gets smoothed. splitting will result in extra verts but on a simple model that's no problem. The best looking solution requires more work (and more polygons). In real life (on things like furniture) there are no perfectly sharp edges, all corners have a small radius which catches the light. If you place additional edges on your table surfaces near the corners Poser will round them but the rounding will be limited to the very edges. Hmmm... too difficult to explain - I'll do a picture soon.