OD&D vs B/X and BECMI

Again, what’s striking to me is how much is the same. I was initially under the impression that AD&D was a compilation of everything OD&D, while the “Basic” strain of D&D was a restructuring by different authors using the same underlying principles. But after cross referencing the source rule books a few times, I’ve come to the conclusion that that’s not the case at all. The rules and information in the Moldvay and Mentzer sets are very similar as what’s given in the three original D&D booklets, just vastly improved in clarity, organization and explanation.

Like the Moldvay set, OD&D basically runs on a d6 system, not just for weapon damage but for resolving success of most situations, such as finding hidden doors and avoiding traps. The d20 is only used for combat resolution on the alternate combat table. OD&D is notorious for how much of its game system is actually not detailed in its core books, and those gaps are filled in by the Basic and Expert sets.

It actually gives me more confidence in considering the whole line of "Classic" D&D rules to be one continuous strain beginning with OD&D and re-edited right up to its last revision with the Rules Cyclopedia.

The modern OSR attitude seems to be that OD&D and B/X/BECMI are two different strains of the game, but I believe that part of that might be driven by an urge for purism in rulesets and a highly elitist attitude among OSR gamers. During the '80s and '90s when these books were in print, there was no distinction between the flavors of Classic D&D since they were all branded as the same, and I think the OSR attitude is an overreaction to that which focuses on the most minor differences in wording and table values.  And this is understandable, since most OSR games owe their very existence to minor differences in wording and table values, and legally could not exist without them.

Coming back to D&D, the high degree of compatibility between the successive versions makes it much more useful to cross reference between them, and to use the information in one book to fill in the gaps of the other.