My view is that they are rubbish for surface swimming, especially for a non-freediver lol
If you are planning on doing front crawl etc I think you'll find them a pain, if you are just snorkelling and kicking with the legs only maybe they'll be fine if you have strong legs but most people would find them too tiring for a long day of snorkelling. I think normal fins would work better unless you need to swim against strong currents etc which for most people is unlikely.
The best advantage for 'snorkelling' is that with freediving fins you'll have better chances of keeping up with sea life but again as Connor mentioned, that's assuming you have strong legs etc.
Overall personally I don't think they're worth the extra $$$ for snorkelling alone, especially if you already have a set of fins. Maybe put the $$$ towards a freediving lesson/course instead
Also seeing as you are from Canada - don't know where you are planning on using them but if it does involve a flight, they can be a real pain to pack as they don't fit in suitcases mostly.