I don’t have any knowledge of these programs, but typically this depends a lot on your exact use case. So if you want to get a good answer, you should probably provide some more information on what systems and for what purpose you want to use these.
Often the argument comes down to: How much metadata about your file are you willing to leak for convenience.
Maybe people say that Volume based are better because they don’t let the attacker know about the size of files or how many, etc… But most people out there aren’t really informed of the risks vs benefits. They just blindly follow what someone else said on a forum somewhere because it sounded smart (without really digesting the info to know if it was indeed even relevant to their situation).
If you are trying to hide a collection of illegal MP3s from the RIAA or movies from the MPAA then indeed this might be a concern. They have fingerprinting programs that can make a reasonable guess what you have encrypted in a folder just by number of files, file sizes, MAC times, etc… But if you have a collection of random docs and spreadsheets that you made (and are thus unique). Do you really care if someone knows how many files and what the file size or last mod date is? Probably not, there’s not much they can do with that data. What you care is that they can’t see the actual data… and most programs are just fine for scrambling that.
Again, just from theoretical “knowledge”: File based encryption could be beneficial in combination with Syncthing as you don’t need to hash an entire volume whenever anything changes. Though your options both are volume based, so your intention may be to sync the unencrypted files while the enc-volume is mounted, in which case this isn’t relevant at all.
Cryptomator uses file-based encryption in it’s “vault” folder, rather than encrypting files to a single container, which in my eyes makes it more suitable to file syncing.