Differences Between Macintosh and PC Versions
Levels
The first major difference is the level design. While the PC version contains 6 episodes with each episode containing 10 levels (1 of those is a hidden bonus level), the Macintosh version (reffered to as the 2nd Encounter) contains 30 levels with no divisions into episodes. The Mac version is divided into floors, but you can not start on a specific floor and every floor has a different amount of levels. A 3rd Encounter was later released for Macintosh containing 60 more levels which were supposed to make up episodes 2 to 6.Obviously, the number of levels aren't the same but this doesn't necessarily mean that the Macintosh version is giving you more. Many of the levels are similar, but the Macintosh levels are usually much less intricate and much shorter. This is apparent in the first level where the path to the exit is exacly the same in both versions, but the PC version contains many more possible side-trips and many more rooms. Other levels in the games are completely different. Basically, the 2 games play extremely differently and offer unique experiences.
Game Engine
Another major difference is in the game engines. At first glance, the Macintosh engine, which is 2 years newer, seems to be the more advanced. The graphics in the Macintosh version are much sharper, clearer, and better looking at twice the resolution of the PC graphics. Also, the game takes up a slightly larger portion of the screen and the sounds are much higher quality in the Macintosh version.However, the enemies in the Macintosh version are only 2D sprites whereas the enemies in the PC version are 3D sprites. This means that the Macintosh enemies only have 1 side, a front side, and thus, they are always facing you. In contrast, the PC enemies have 8 sides, making for much more realist play; in the PC version, it is possible to sneak up behind guards and kill them before they see you - something that can't be done in the Macintosh version.
The enemies in the PC version also offer an extra level of realism by being able to patrol an area. In the Macintosh version, the enemies will just stand in one spot until they see you or hear you; in the PC version, enemies will stand in place or patrol an area until they see or hear you. These differences make the PC version's game engine more advanced despite being 2 years older.
Weapons, Items, and Enemies
Several other difference worth noting include the addition of 2 extra weapons in the Macintosh version: the flamethrower and the rocket launcher. Those two weapons and some other items (bullet crates, flamet thrower and rocket ammo, backpacks) are not found in the PC version.Also, some other pick-ups and dropped items are different. For example, in the PC version, dropped clips give 4 ammo and other clips give 8 ammo; in the Macintosh version, all clips give 5 ammo. Also, picking up treasure in the PC version adds to your score (40000 points gets you an extra life); in the Macintosh version, picking up treasure increases your item count by one until you get an extra life at 50 items.
Other differences include an additional enemy, the Flying Hitler, in the PC version and different bosses in the 2 versions (see the enemies and bosses pages); the Mac version actually uses some bosses from Wolfenstein 3D and some bosses from Spear of Destiny.
Miscellaneous
Yet another difference is that changing the difficulty level in the Macintosh version only affects the damage taken and starting ammo whereas in the PC version it affects the damage taken and the number of enemies; the PC version tends to be much more difficult. The Macintosh version also has an auto-map that is helpful in finding you way around; there is no mapping feauture in the PC version.The last difference I can think of is the pools of blood in the PC version. In the Mac version, you only have pools of water - no pools of blood. If your health is less than 11 in the PC version, you can drink the blood to gain back some health.
Other Versions
The Atari Jaguar version was a direct port of the PC version.There was also a Super Nintendo version of Wolfenstein 3D released; it was a cross between the PC and Mac versions. For example, the flamethrower and rocket launcher from the Mac verison are present as is the abilty to sneak up on enemies from the PC version. Unfortunately, it was extremely censored through the changing of the guard dogs into rats and removal of the Natzi symbols.
Released in 2002, the Game Boy Advance version is an nearly exact port of the PC version. It contains all 6 Episodes. The only difference is that you can only save the game at the end of a level - not during.