That style gearcase isn't faster by nature. The shape of the gearcase isn't for speed its to prevent an extremely dangerous condition called blowout. Most manufacturers gearcases are subject to blowout at speeds approaching 80 mph. So its something the average Joe doesn't have to worry about. Here's the one that runs people ragged.
Today there are a number of great high performance props on the market.
But what runs great on your buddies Bullet might be a dog on your Champion. Let me state this very clearly. Each different hull design on the market has its own unique lift characteristics and requirements. There is only one rule in prop selection. If you cant find a dealer who will let you run the prop before buying it keep looking.