What were the differences?

Depends on the White Box and the B/X version.

There were multiple "B/X" rulesets from the Blue Book to the Red Box to the Big Book, and all were "more basic" than AD&D 1e, but AD&D 1e is really just all the 0e books (the core plus the supplements) rewritten into the three core AD&D books.

The original 0e - as defined by the first 3 books published in 1974 - isn't radically different than what you'd find years later in the Blue Book (or Red Box), but those later books (like Old School Essentials today) did a better job at explaining and presenting things. AKA, the value of later drafts and hindsight.

However, if you really want a detailed breakdown, ask over on Dragonsfoot.org because there you'll find TSR archeologists who will define what exact changes occurred.

As I have run 0e (+ houserules) for many years, I find them all "close enough" that in actual play, the only thing my players note is I use "race as class" and otherwise, they refer to the game as AD&D half the time.

OD&D?

Lets see.

The biggest difference is BX does race as class. So Halfling was a class for all intents and purposes.

Similar 3d6 in order then swap a few points around system for chargen.
In OD&D Clerics could swap 3 STR for 1 WIS, Fighters and Clerics could swap 2 INT for 1 STR or WIS respectively. Magic Users could swap 2 WIS for 1 INT and Fighters could swap 3 WIS for 1 STR.
In BX it was a straight 2 for 1 swap. STR could be lowered to raise a Cleric or MU's prime stat. INT could be lowered for any but the MU and Elf. WIS could be lowered by any but the Cleric.

In BX Stats do a bit more. But the bonuses are in some cases not as high.
In OD&D a DEX of 13 or better was +1 to hit ranged. while 8 or less was -1. CON of  15 or more was +1 HP/level while 6 or less was -1. CHA ranged -2 to +4. Nothing for STR, INT or WIS.
In BX All stats but INT and CHA had a range from -3 to +3. INT instead determined how literate and linguistic a character was. While CHA ranged -2 to +2. STR now effected melee damage and open doors, WIS for saves, DEX now effected also initiative and AC.

HD in O was a d6 for every class, while in BX it was similar to AD&D.

Spells go only to level 6 and the listed levels ranged from 8 to 16 for various classes on OD&D.
While in BX they were capped at 16 with some guides for DIYing more levels till the never produced Companion set came out.

Weapons in both do a flat d6. But X of BX introduced optional dice for some weapons.

Theres more but those came to mind right off without having to do heavy comparisons.

On a blog I was reading recently, the author asserted that the "3 for 1" ability score adjustment for 0d&d wasn't an ability score swap; it was rather a way to show that other abilities contributed to a character's experience gain.

A Cleric with a 15 STR and a 12 WIS could consider his WIS to be a 14–for the bonus to XP gained only. If the Cleric also had a 14 in INT (which, I believe, is a 2-for-1 calculation), then the cleric's WIS score was considered to be 16, which gained him the 10% XP bonus. The Cleric didn't lower his STR and INT scores to raise his WIS score, as in B/X and BECMI.

Quote from: cavalier973 on June 24, 2021, 01:08:01 AM
On a blog I was reading recently, the author asserted that the "3 for 1" ability score adjustment for 0d&d wasn't an ability score swap; it was rather a way to show that other abilities contributed to a character's experience gain.

A Cleric with a 15 STR and a 12 WIS could consider his WIS to be a 14–for the bonus to XP gained only. If the Cleric also had a 14 in INT (which, I believe, is a 2-for-1 calculation), then the cleric's WIS score was considered to be 16, which gained him the 10% XP bonus. The Cleric didn't lower his STR and INT scores to raise his WIS score, as in B/X and BECMI.

My first thought was what? That's a load of crap. So, I went back and read it. You can certainly take that idea from the reading if you remove later editions from interpretation. It's an interesting way to look at it.  The vagaries of OD&D are part of its charm.

Quote from: Tristan on June 24, 2021, 01:14:51 AM

Quote from: cavalier973 on June 24, 2021, 01:08:01 AM
On a blog I was reading recently, the author asserted that the "3 for 1" ability score adjustment for 0d&d wasn't an ability score swap; it was rather a way to show that other abilities contributed to a character's experience gain.

A Cleric with a 15 STR and a 12 WIS could consider his WIS to be a 14–for the bonus to XP gained only. If the Cleric also had a 14 in INT (which, I believe, is a 2-for-1 calculation), then the cleric's WIS score was considered to be 16, which gained him the 10% XP bonus. The Cleric didn't lower his STR and INT scores to raise his WIS score, as in B/X and BECMI.

My first thought was what? That's a load of crap. So, I went back and read it. You can certainly take that idea from the reading if you remove later editions from interpretation. It's an interesting way to look at it.  The vagaries of OD&D are part of its charm.

I think the idea was that a strong and smart and wise fighter would gain XP more quickly than a fighter who was merely strong (or, as quickly as a fighter who was exceptionally strong).

Quote from: cavalier973 on June 24, 2021, 02:01:03 AM
I think the idea was that a strong and smart and wise fighter would gain XP more quickly than a fighter who was merely strong (or, as quickly as a fighter who was exceptionally strong).

Oh, that's definitely the interpretation I see there based on the wording.  In B/X its very clear this isn't the case. "This adjustment shows that a character may practice hard and learn how to fight or reason well, but at the cost of not developing another ability."  This is also in the Holmes edition with different wording.

I like the OD&D interpretation mentioned above. It's more interesting.

Then again, if you read the following: "Prior to the character selection by players it is necessary for the referee to roll three six-sided dice in order to rate each as to various abilities, and thus aid them in selecting a role."

'in order' does not come across as meaning sequential, but more in 'for the purpose of'.  It fits with what is written in B/X "Roll 3d6 (for a result of 3-18) for each ability and put the result in pencil next to the name of the ability.

So many rulesets, with D&D on the label.

There is definitely something really fun going on in White Box 0e D&D.  It may not be the perfect ruleset.  Heck, I don't know; but it's fun gameplay.   I've never been exposed to B/X D&D, but the OSR is in love with it; for sure.

Quote from: Tristan on June 24, 2021, 11:40:18 AM'in order' does not come across as meaning sequential, but more in 'for the purpose of'.  It fits with what is written in B/X "Roll 3d6 (for a result of 3-18) for each ability and put the result in pencil next to the name of the ability.

Yeah, this has been my group's interpretation of the rules since day 1, I think. It's interesting to see how many folks interpret "in order" as sequential. Only. No discussion.

I am definitely thinking about snagging the 0d&d pdf off dndclassics, now.

Wasn't another difference between 0d&d and "Basic" the lower level limits for demihumans in 0d&d? Like, halflings topped out at level 4, and dwarves at level 6?

Also, elves in Basic are a little easier to play, being essentially the fighter/mage multi class character, but with the ability to cast spells while wearing armor. In 0d&d, I think elves had to decide whether to act as a fighter or a mage at the beginning of each new adventure.

Quote from: cavalier973 on June 24, 2021, 06:33:45 PM
I am definitely thinking about snagging the 0d&d pdf off dndclassics, now.

OD&D is definitely worth a read. Crude layout and art, very scattered organization, and there's a lot of vagueness that leads to alternative interpretations (including demihuman classes). But the tone is radically different than later editions. More inspiring. Though OD&D includes parts of Chainmail by reference, so you might want to grab that as well.

Quote from: Pat on June 24, 2021, 06:54:41 PM

Quote from: cavalier973 on June 24, 2021, 06:33:45 PM
I am definitely thinking about snagging the 0d&d pdf off dndclassics, now.

OD&D is definitely worth a read. Crude layout and art, very scattered organization, and there's a lot of vagueness that leads to alternative interpretations (including demihuman classes). But the tone is radically different than later editions. More inspiring. Though OD&D includes parts of Chainmail by reference, so you might want to grab that as well.

I just purchased it, a few minutes ago. Scanned through the first two books and part of the third.

I have made my own dungeon, using the Mentzer Basic rules, and ran my kids through part of it. I would like to have them finish it, but I work so muc h I don't have the time. I am interested in how these books advise dungeon building.