I'm surprised to see such a size difference between the L and XL. They don't even look like the same fin .
I just started using Jet fins. I bought a cheap used pair to see what all the fuss was in the whole split fin vs. more traditional designs.
I love the fact that they're so much smaller. My old Tusa split fins barely fit into my SCUBA bag's fin compartment.
I added spring straps to my Jet fins, which make the extremely easy to put on and take off. With my Tusa's, I had trouble climbing the boat's exit ladder.
So far, I feel like the Jet fins have a good thrust and are very "responsive" in the water. For travelling a long distance at a steady pace, my Tusa split fins were a bit more effective. It seems like I could get a nice, easy momentum going with the Tusa's.
However, my Tusa's are HUGE compared to the Jet Fins, and the difference in their effectiveness in the area of gaining a steady momentum (something I don't need to do very often) was relatively small.