One of the funny things about the Holmes-edited D&D rulebook is that expressing a strong preference for it is as likely to get elicit a cry of "Nostalgia!" from AD&D partisans as it is from devotees of more recent editions of the game. I can only assume that this viewpoint has something to do with the belief that Holmes is nothing more than an introduction to AD&D and that seeing it as a unique game in its own right is somehow mistaken.
It's certainly true that the text of the Holmes rulebook frequently directs readers "who desire to to go beyond the basic game" to AD&D, but, as Holmes's preface also makes clear, this version of the rules is strongly based "upon the original work published in 1974 and three supplementary booklets," but re-written with the aim of "introducing the reader to the concepts of fantasy role playing and the basic play of this game." A close reading of Holmes quickly reveals that the game is deeply rooted in OD&D, deviating from it only in a few places, only some of which have any connections to the then-far-from-finished AD&D. I haven't done a formal survey, but I'd guess that most of its deviations (such as its interpretation of magic missile and DEX-based Initiative to cite but two examples) are purely Holmes's invention (or that of others in the gaming circles in which he moved at the time). Taken together, this gives Holmes a unique flavor of its own, one that was compelling enough that I was forever hooked on D&D.
Another thing about Holmes that can't be underestimated is the way that it presented itself. Though basic in its scope, it didn't talk down to its assumed readers, whom the box cover proclaimed to be "adults." Much as I love Moldvay, its presentation is less sophisticated to my eyes and, more specifically, less hobbyist, by which I mean that there are fewer rules lacunae for referees to adjudicate according to their own lights. This difference in tone matters and, especially nowadays, I find myself drawn more and more to Holmes, which occupies a nice middle ground between the glorious mess of OD&D and the glorious fastidiousness of AD&D. It really does have its own unique voice and feel and it's a pity that, even in this time of the old school renaissance, its virtues are not more widely recognized.