The question isn't what fin is best overall but which fin is best for you. Many people on this forum rave about particular styles and brands because they have discovered the kind that suits them best. That doesn't mean that they are best for you. To find out what is best for you, you need to run through various criteria. You may also have to beg and borrow a number of fin types and try them out to narrow down the choice, so that you don't make an inappropriate, painful and expensive selection.
Start with the footpocket and consider fit and comfort. Many divers here are strong advocates of open-heel fins and dismiss closed-heel fins as warm-water wear. They will argue that open-heel fins offer more protection, because they are generally worn over a suit, socks or other footwear. But closed-heel fins can be worn with protective footwear too, they don't have to be worn over bare feet. The closed-heel Apollo fin is meant to be worn with protective footwear. If you get the chance, try both open and closed-heel fins and see which suits you and the activity you are using them with. What matters is fit and comfort. The fins shouldn't be too tight or too loose. Remember that fins do come in different sizes, but only one width. Trying them on first is therefore a good idea.
Now the blades. The earliest skin divers used short blades, and this is also the preference of modern bodyboard surfers, who of course swim on the surface of the sea in choppy conditions. Such fins give them manoeuvrability, which is also an advantage when fins are used in snorkelling and the idea is short light bursts of finning rather than sustained speed. Endurance is also likely to be something you want to consider when snorkelling or distance swimming. Traditional full-foot training fins with soft, short blades are popular with swimmers because they provide exercise without tiring or cramping the wearer. And yes, do consider long-bladed fins too, which free divers appreciate because they need the option of raw speed to get them down into the depths as quickly as possible.
What you need to do is to define the problem you have set more carefully. First, what exactly do you mean by snorkelling? Is this going to be a gentle activity where the point is to observe what is going on beneath the waves and to make a few, simple forays below the surface? Or are you planning to go chasing around after sealife, expending lots of energy? Different fins are appropriate for different purposes. Just as there isn't such a thing as a "one-size-fits-all" fin", there isn't such a thing as a universal, all-round fin; those that claim to be the latter are effectively a compromise. Power fins are going to be very tiring if used over an extended period. Fins that are good for manoeuvrability or endurance won't give you the turns of speed you may want at certain points in your snorkelling or distance swimming.
So it's over to you again. To sum up: find out which fins fit you best first. Consider whether you want to wear them barefoot or over foot protection. Consider what kind of water activity you are planning before deciding which stiffness and length of blade suits your purpose. And, for the record, I prefer simple, traditional, full-foot, medium-bladed rubber fins when I go snorkelling in the North Sea. They fit perfectly over my drysuit and match the gentle floating and occasional slow underwater forays I do. Your priorities may well be different and you will therefore choose other kinds of fins. Don't just follow the crowd, follow a more precise definition of your problem through to its solution. You won't regret your eventual choice then. Fins are a very personal item of gear, just as masks are.