I think dat:// is a much more promising protocol over IPFS. The developers don't seem to delude themselves as much to the capabilities of the archive and there is no ICO. They advertise it as it is; Torrents with updates via public keys.
ipfs:// on the other hand I hear most frequently handwaving away the problems like "who will pin unpopular content" or "how far does it scale" or "who will pay for gateway bandwidth once it gets big" or even "how to make content easily update" (I don't consider IPNS a good solution to that question)
I was going to post just this. While I'm very skeptical that either of them will become popular, dat seems to be more suited for publishing websites and sharing large files. For a website it's nice that you share the whole site and are able to update the content while keeping the link (it's possible to tell if the content has changed, but there is no version history). And dat is already my first pick whenever I need to copy large files privately over internet.
Since then I've used dat for copying files a couple of times. I haven't really browsed the dat:// web and I'd guess nobody has visited my website over that protocol (but then I don't have analytics and estimate my blog to have a dozen visitors a month).
>who will pay for gateway bandwidth once it gets big
That's only a problem because IPFS isn't "big" enough for browsers to ship with an IPFS gateway integrated in them.
IPFS will need very big gateways because until that happens IPFS needs to grow a lot. And even then I doubt browsers would just ship a P2P application to autostart with the browser to the consumer.
ipfs:// on the other hand I hear most frequently handwaving away the problems like "who will pin unpopular content" or "how far does it scale" or "who will pay for gateway bandwidth once it gets big" or even "how to make content easily update" (I don't consider IPNS a good solution to that question)