My current kart has a groundspeed of 3/6 and an airspeed of 3/6. I'm assuming this means my top speed is the same for when on land and while gliding. Therefore, it would make sense that it doesn't matter whether I take an air path or a ground path.
So, the question is: in places where there's a glide section and a ground section that share the same path, and your airspeed and groundspeed are equal, is it better to keep the glide going for as long as possible, or to dive for the ground and cut it short? Does it matter at all? A good example of the situation would be the forest section of Rock Rock Mountain/Alpine Pass.
A more interesting situation occurs in DK Jungle - there's a gliding section above a water section. My kart has a waterspeed of 4/6. It doesn't feel like I save any time by diving into the water (or stowing the glider) instead of gliding over it, but maybe that's due to the angle I dive at or something. In theory is it even possible for it to help?