They are very different processes. Vapor smoothing is more of a hack than anything. It traps the solvent in the part for a very long time. Like using acetone on auto body trim and bumpers that are mostly ABS will get you fired from any shop. It will bleed and ruin the top coat an clear coat as it vents from underneath them. In my testing, acetone greatly alters the structural strength as well. Polishing maintains or in some cases improves the mechanical performance of parts. Even for cosmetics, the polished part will look like it was injection molded while the inconsistency and rounded corners of vapor smoothing look very DIY. Polishing can be done poorly, and I am an actual finishing pro, so YRMV.