OD&D without supplements is the ideal "semi-freeform make it up as you go along" game, which gives you just enough guidance to set a baseline and some assumptions about what the game-world is like but otherwise leaves everything up to the individual players and referee. On the downside, this version is almost impossible to comprehend if you don't have a firm grounding in later versions of D&D (or don't care about later versions of D&D and are willing to make it up as you go along and not care if you're consistent with the actual intent of the rules which, in this edition, is a perfectly valid approach)
OD&D with supplements is pretty much 1E AD&D with less organization and worse balance. Bits and pieces from the supplements (an/or The Strategic Review and The Dragon) can enhance the game or help focus it in a particular direction, but (IMO at least) if you're going to use all (or even most) of the material from the supplements you might as well just play 1E AD&D
The Holmes (1977-78) Basic Set is wacky -- the rules are kinda OD&D, kinda 1E AD&D, and kinda their own thing, and since they only cover levels 1-3 you're eventually going to have to do so some kind of conversion. That said, it's still my favorite introductory version of the game, which IMO captures the spirit and feel of what I like about D&D better than any of the later Basic Sets (part of this is undoubtedly the Sutherland, Wham, and Trampier art -- my favorite era of TSR/D&D art)
The Moldvay (1981) Basic Set and Cook/Marsh (1981) Expert Set are the most concise presentation the rules have ever had, but IMO they're ironically almost too slick -- this is the version that begins to feel mechanical and formulaic to me, like the limitless possibilities of the original game have been narrowed down and constrained. With the original game I feel like I can do anything (as player or referee); with this version I feel like I can do "anything" (provided it fits within certain formulae and parameters). That said, for casual and one-off play this version is hard to beat; this is, as its partisans on dragonsfoot have described it, the "sit your butt down and start playing" edition.
The Mentzer (1983) Basic & Expert sets are essentially (~95%) the same rules as the above, but reorganized to make introducing the game to absolute novices easier, and to tone down progressions (spells, saving throws, and thief skills) at the higher Expert levels to allow room for growth in the Companion and Master sets. As a kid in the 80s, my friends and I used these two versions interchangeably, never realizing there were any differences between them besides the artwork.
The Rules Cyclopedia compiles all 4 Mentzer sets (Basic-Master) plus the General Skills rules from GAZ1 and some new stuff, into a single book, without all the handholding advice and sample adventures and such. It's the second most concise treatment the game has ever had, losing out to the Moldvay/Cook/Marsh edition only because it's got a lot of optional stuff (General Skills, Weapon Mastery, etc.) and high level stuff (since the book covers all the way to level 36) cluttering up the otherwise simple core rules. (It's perhaps also worth mentioning that I don't particularly like the optional and high-level stuff.)