Like anything, there are good designs and not so good designs; plus there are always going to be elements that are subjective, personal, and/or dictated by conditions, etc.
I am strictly a tropical warm water recreational diver. I used to have a pair of the 1st generation of Atomic's full-foot split fins. Performance wise; they were great and were perfect for travel, but were not very comfortable. Eventually Atomic reformulated some of the compounds, along with slight changes in the ergonomics to make them more comfortable and better able to hold their shape. Sadly, these 2nd generation versions, which looked essentially the same, were a total disaster IMHO; horrible in just about every way. Also had some open heel Apollo Bio Fin Pros too, which were very good performers (probably the fastest fin I have ever used), but were pretty demanding on the legs and just way too heavy. Tried a few other splits, but never could find anything that worked for me. So, started testing paddles and found that I was having similar problems finding the right combination of traits to suit me. Even tried free diving fins for a time.
After a while I started to notice that no matter what destination I went to, many of the DMs very specifically used the Mares Avanti Quattro Power full-foot. So, gave them a try and haven't looked back. To this day I still get comments from operators and DMs that say these are the best full-foot fins for tropical boat diving ever made, and I have to agree - they are fantastic performers. Despite the fact that they are expensive, large, and not the best for travel, I am so sync'd up with how they perform I don't think I could ever go back to splits, or anything else for that matter. Generally speaking, paddle fins just seem to have a more "connected" feel that I personally prefer.
I guess the bottom line here is there really is no right or wrong when it comes to fin design; it's more about what works for you personally within the context of the conditions you dive in. Opinions and reviews aside, the only true way to find out is to find some products that interest you and give them a try in real-world conditions.
Hope this is helpful.