Like everyone else, I read this because H.P. Lovecraft praised it so highly. The theme is very much in the vein of Lovecraft, and the supernatural elements are treated very lightly, as is the case in the above-average Lovecraft stories. The Willows is a well-crafted tale, and given this single data point, I have to say that Blackwood is by far the better stylist.
Overall, I think weird fiction is not quite my thing. It comes close at times, but I much prefer Dracula, or the novels of Charles Williams. Worldview seems to play a big part in what we find frightening, or compellingly numinous.