Looking through tunebooks there does not seem to be total agreement as to whether to notate hornpipes dotted or undotted. However my observation is that the majority notate them undotted. That's my preference FWIW and that's how I notate them. For the reasons given above - that the degree of dotting varies between players.

As an interesting aside, at a session the other day, someone produced the dots for a jig (I can't remember the title) but it was claimed to be a Morris Dance tune. When they started playing it the tune was clearly "Roxburgh Castle" which I have heard played both as a hornpipe (dotted) and as a reel.

Thus do tunes evolve.