Mike -
Adam mentions the topography of Eastward Ho. Fowler thought the specific site -- and Cape Cod in general -- was ideal for golf. I think CB Macdonald had also looked at Cape Cod as the ideal place to build NGLA, except that back then it was too remote, i.e. not enough of the men with the money would make the trek.
Here's a link to a 1921 article by Fowler that basically gives a hole-by-hole description of the course. (For those who know Myopia well, it might mean something, comparatively speaking)
www.la84foundation.org/SportsLibrary/GolfIllustrated/1921/gi156p.pdfOther than that, I don't know how to compare it with Myopia. (I sure like the photos I've seen of Fowler's work there and other places.) But in reading the old articles from the late 20s and early 30s, it's striking that while Eastward Ho gets much acclaim (and in one old ranking is tied with Myopia as the best in the state), Myopia's status as one of the 'foundational' courses of American golf -- and Leeds' work there -- tends to put it in another class. I cut and paste a snippet that focuses on Leeds:
"The Greater Boston District has another club [i.e. along with Brookline], the Myopia Hunt of Hamilton, Mass., which played a major part in the early history of the sport in this country, venue of four National Open Championships between the years 1898 and 1908 and a golf course which, with undoubtedly fewer major alterations in more than thirty years of any first class course in the land, still measures up with the leaders, because its "father", the late Herbert Leeds, was years ahead of his time in the art of laying out golf holes of character.
It was pure innate love of the game, as an amateur, that sent him abroad to study the most famous holes of the renowned British courses to help mould his ideas of what he wanted at Myopia. And the club was wise enough to give him a free hand in the pursuit of those ideas. He held a place as an amateur golf course architect comparable to that enjoyed in later days by C. B. Macdonald, builder of the National Links at Southampton, L. I. In the early years of golf in this country, visitors by the scores visited Myopia to get advice and ideas for their own clubs."
Peter
PS - another article -- maybe by the same writer -- also stresses Leeds' foresight and understanding of sound principles, and notes that most of the few changes over the years had to do with adding more bunkers...which strikes me as interesting in and of itself, i.e. the role/function of bunkers back then