They are a bit stiffer than the regular sea wings, but not as much as you would think or probably hope.
I used a pair briefly (sorry, sold them off a long time ago) but I did not like them. The stiffer blade does not track as well through the water as the regular sea wing, and in my opinion the sea wing itself was pretty marginal in terms of stability and tracking. At it's best the sea wing was not great at alternative kicks and the gorilla fins were worse. I also hated the way the sea wing in general trapped line in the corner where the blade angles out from the foot pocket.
In short both the Sea wing and Gorilla fins were two of my many unsuccessful attempts over the years to try new fins and find a fin that was superior to the Jet Fin.
If you want more power, go with an XL sized pair of Jet Fins. My wife has mens size 9 feet and the XL Jets fit fine with a 7mm wet suit boot and they also fit my 10 EEE feet with 7mm wet suit boots, so they will accommodate a fair range of sizes other than skinny size 12 feet.
My wife switched from a pair of large Sea Wings and was amazed at the increase in both speed and power that occurred with the XL Jet Fins and their longer blade. She used to complain that I swam fast even in doubles, but now she is herself very hard to keep up with.
The Jet Fin is a 40 year old design, but it is still an exceptional fin and is badly under rated by everyone except those who use it. It offers superb power for doubles, and is also a very efficient fin overall in terms of speed, ability to perform alternative kicks without straining knees or ankles, and in close quarters maeuverability. It does everything very well and that is the reason Jet Fins are still cataloged while other SP fins are not. Personally, I am pretty sure the Jet Fin will outlive the current generation of fins just like it has the last few generations of fins. In that regard it is sort of the B-52 of fin technology.
