Thank you for your feedback! It's true that it's similar to those two services, but, in my opinion, it's different enough to have its own space.
As for registration, don't you need to specify a username when you use instapaper? The problem with using historious without an account is that some features won't work, plus you won't be able to access your account from a different machine/browser. Many users have requested it, though, so I'll try and make it happen!