First, snapdrop shouldn't be used at all, it was sold to LimeWire along with some other similar P2P sites (sharedrop, easyupload) so only https://pairdrop.net/ can be trusted.

The difference is that localsend has dedicated apps as well, but sometimes you just quickly need the web version and for me https://web.localsend.org/ is often too slow to connect or devices can't see each other, meanwhile https://pairdrop.net/ always work.

LocalSend doesn’t work for non /24 subnets