The Horsa was a very large Glider with seating for 30, compared to the 13 seater Hadrian. In-game the Glider only delivers 4-5 troops, which is less than even the 8 seater Hotspur, which was only used for training. The Horsa is the largest "unit" in CoH beating out the Hamilcar from CoH1 (which was shrunken down considerably), the Jagdtiger is the size of one wing! The only thing longer is the unused Soviet "Steam Train" in CoH2. As the Horsa is the size of a small territory point, this makes it impossible to land without damage, and very easy to spot. When it "dies" it bursts into several dozen gibs, dirtying up the map and causing lag for some players.
The Hadrian in comparison would have made more sense for small troop drops, and gameplay wise would be easier to land and not scatter a million gibs everywhere on death. In the end I have to wonder why they chose such a massive Glider in a smaller Glider would be easier on both players and their computers.