The pro is my favorite for underwater swimming of the slower/relaxed/meditational type of swim. I may actually prefer the classic for fast surface swimming or sprinting underwater, as once it gets cooking it works quite well. As I do not have any opportunity to work on distance much (no buddy, haven't been to a freedive certification course, etc.) I use the underwater swimming time as my relax time. Sometimes I will first just sink to the bottom and lay there a few seconds, then gently push off and see how peacefully/smoothly I can glide through the water. To me, it's a bit like underwater yoga or something! The Pro works wonderfully for this. I think my son preferred the Classic flukes, as he is faster with them. It may be because they permit a cadence closer to his normal butterfly cadence. He still loved the Pro flukes though!