I don't know anything about Spellcraft & Sorcery; I've never heard of that one. I can give you some info on the other two, though.
There are two versions of
Swords and Wizardry: "Core" and "White Box." Core is currently available in Word DOC format, and will be available as a PDF or POD very soon. White Box is still being worked on, but is nearing completion.
S&W:Core is similar to the 1974 "0e" rules with some additions from later rules supplements. Hit dice are slightly different, but remain d6 based. Monster hit dice are d8. Other differences include saving throws (S&W uses a "single category saving throw"), slightly different prime requisite bonuses, different XP charts (although they're similar), different (but low-powered) attribute bonuses, and a "flip-AC" system (you choose which approach you prefer: high=good or low=good). It has expanded spell lists and monsters (i.e. includes material from the supplemental rules), and uses the supplemental rules for XP awards. Weapons do variable amounts of damage. Monsters do too, and may have multiple attacks (e.g. claw/claw/bite).
S&W:White Box is similar to the 1974 rules without additions from later supplements. All hit dice (monsters and PCs) are d6-based. It, too, uses the "single category saving throw." XP progression is slightly different. Ability bonuses are closer to the original 0e rules. Spell lists are similar to the 0e rules, without some of the spells from later supplements. Monsters typically have a single attack and do d6 damage, with a few exceptions. The "flip-AC" system is used.
Spellcraft & Swordplay is less of a retro-clone than Swords & Wizardry; it's more like a "inspired by, but expanded and re-imagined" set of rules. It starts with an OD&Dish foundation, but instead of using a d20-based combat system, Spellcraft & Swordplay adopts a combat system inspired by (but not a duplicate of) d6 miniatures combat rules (thus, similar to OD&D using
Chainmail combat rules, rather than the d20-based "Alternate" system).