The fin v long keel argument is pretty much like the anchor debates - people generally advocate what they have themselves.
One thing that really distorts the arguments is displacement. You seldom if ever see a light displacement long keeler but some of the supposed benefits of long keels are really benefits of heavy displacement. A straight comparison of a well-designed heavy fin keeler and a long keeler of similar displacement would I'm sure produce a quite different view.
One hull good, two hulls better.