I am not 100% sure that the regular blade will perform better under these conditions than the Gator. It has just been my experience that the Gator performs much better when you are discharging.
The Gator is designed to lift the grass as it is cut and redirect it back toward the center of the blade. This action continues to take place until the clippings are very fine. With a mulch plug in place on some decks this does not happen very well. As you keep all of the grass under the deck you naturally have to mow much slower.