One of the first tips I can share about fins is there not called flippers, now we have that covered lets move on. In my five years of diving I am up-to my fourth pair on fins. From these four I regular cycle between two, the the others gathering dust. From my experience the best fin is comfortable, sturdy and not too long. Additionally, it is open heal preferably with spring straps. It is important to use open heel designs for two reasons, wearing a boot provides extra warmth, even in the tropics and extra protection when doing shore entries or walking around a crowded boat. Excessively long fins end up just getting in the way, I once purchased a ridiculously long pair of fins that were some sort of hybrid open heel/free diver style. I used them once and I wasn’t even able to on-sell them. Spring straps are important because they are just so convenient, when you have a full kit on they are like a dream to don.
Ill be honest, I have never tried split fins so I wont discourage you from purchasing them other than to tell you to try them yourself. I have always avoided split fins due to their cost, as they are always at least double the price of a single piece fin.
My fist pair of fins were Oceanic Vipers, I still consider them a decent fin and they were inexpensive. My third pair of fins after the ridiculously long pair were the Hollis F1 Bat Fins, these fins are amazing, they are sturdy and beautiful to frog kick with. The only negative is they are terrible for surface swims. I made the mistake of using these fin on my IDC, my training to become an instructor. During this course there is a fair amount of surface swimming to be done, and I can tell you now these fins were almost the death of me. Imagine trying to frog kick on the surface for 800 meters whilst all your peers finished 10 minutes before you.
When Hollis released the F2 I was intrigued. Luckily my lovely wife decided to buy them for Christmas for me. Originally I expected these to be travel and summer fins, although now I am finding myself using them in the middle of winter in a dry suit. They are just lovely, light, easy to don and a decent price. I dont feel like they have the same thrust as the F1 but when you are diving, what’s the rush?