When reading this topic, I think about ancient WRPGs, like Wizardry, Ultima, Bard's Tale, and Might and Magic.
With games this old, we see some of the following things with respect to ports:
* Different computer versions have different bugs and other quirks. For example, 16-bit Bard's Tale 3 (DOS and Amiga) are incredibly buggy to the point where I can't recommend them, despite that game being one of my favorites. (Play the Apple 2 or Commodore 64 version, or look for a patch that fixes the most serious issues with the DOS version.) The Apple 2 version of Wizardry 1 had some quirks, including a famous exploitable bug, that is not found in other versions. The Amiga version of Ultima 3 gives rangers faster MP regen and has accuracy affected by party position (not to mention an RNG that doesn't feel random); the DOS version lacks music and has a very low overworld enemy spawn rate.
* Sometimes, hardware capabilities can account for differences; not all the microcomputers back then were equally capable. The IBM PC, for example, was actually behind other computers of the time until the others died out; only then did IBM PCs catch up and even exceed the capabilities of other computers (and even then, there are still some things other computers did better).
* Console ports were typically quite different from the computer versions, in particular having re-done graphics and adding or replacing music. Wizardry and Might and Magic games were similar to their computer counterparts (but stay away from Might and Magic 2 SNES; the game has severe bugs that make me wonder how the game got released). Ultima games were quite different from their computer counterparts, especially the NES versions of 4 and 5. (NES 4 is worth playing, though if you want a more faithful console port there exists a Sega Master System version; NES 5, on the other hand, is not.) Bard's Tale was also changed drastically; I don't know how good those ports are. There exists a Famicom version of Dragon Wars, but I don't know how that version compares to the computer versions (the game is only in Japanese, and the only change I know about is to replace that one computer you get with, I believe, a Famicom Disk System or something like that).
* The situation with console ports, needless to say, was very different back then; in extreme cases, they could be argued to not be the same game. (And in any case, what happened with MM2 SNES and U5 NES?)