It looks to me like both blades are arched about the same amount in the center, with the only difference being in the length of the arched area. The only real way to know if there is a difference for aure is to lay them both on a nice flat surface and measure from the bench top to the top of the arch on each.
The one you call a medium lift looks like it might have about as much lift to the sail as the high lift does, but that's really hard to tell from the pic. It does look like it has a longer cutting edge which theoretically should help leave a cleaner cut. IME though, you need all the lift you can get for bagging and nowhere near as much to mulch well.