What are the differences between Vampire: The Masquerade first and second edition?
I have both the second and the third edition, but have never played/read the first one.
The most important changes in rules I can think of are:
The traditions themselves are the same (word for word IIRC), but I suspect the promotion of the Masquerade to First Tradition reflects further development of the concept and details of the Camarilla through 1991-1992. Or maybe someone just said, "hang on a second, the game isn't called Vampire: the Hospitality".
They're also slightly different in Dark Ages, but that represents a different culture of Cainites rather than White Wolf changing their mind.
I think the "Cavalier" Archetype was in the 1st ed rulebook but not the 2nd, there may have been some other differences in the lists. Also, Willpower regeneration through Nature worked slightly differently. In 2nd ed. the Storyteller awards 1-3 points, whereas in 1st ed. each Archetype stated a fixed number of Willpower points regained when it triggered.
The hierarchy of sins is different. 1st ed. has "accidental wrongdoing" and "purposeful wrongdoing" at the top, instead of "selfish thoughts" and "selfish actions". It also has "wanton destruction" at 5 rather than "property damage". Ofc you're supposed to apply your own common sense and personal morality, but I always felt the wording "property damage" needlessly left open the interpretation that graffiti or snapping a lock is more liable to free the Beast than involuntary manslaughter. I guess there are real-world moral philosophies by which that is exactly the case.
A fair amount of 2nd ed. text is taken more-or-less unchanged from 1st ed., though.