Topic.

LOL surprisingly hard question to answer. There is 3 different versions of Resident Evil 1 on PSN and their is regional difference between Japan and the international releases, such as the Japanese version's being easier.

Depends on the version of Resident Evil and which PSN store you are purchasing from (America or Europe)

If its just the original Resident Evil on PSN, then the differences would be

Jill does not need to use Ink Ribbons on the PC version to save the game, (at least not on first playthrough)
The PC version is uncensored and in colour.
The audio of the PC will be of lower quality than the PSN version.
The costumes you unlock at the end of the game are different.
The PC version has 2 exclusive guns you can unlock.
The PC version allows you to skip door openings.
High resolutions supported compared to the original PlayStation resolution

If its compared to the Directors Cut PSN release which I believe is what's available in Europe and Japan
The PC version will run at 30FPS as will the Japanese version of the Directors Cut but in Europe it will only run at 25FPS.

The PC version will lack the features of the Directors Cut. There are
An additional set of unlockable costumes.
Some minor graphics changes (like a redesign of the gun)
3 difficulty modes. Training (easy mode)
Original/standard (based on the difficult of the original Japanese release)
Arranged mode: mixes up puzzle items, health, enemy locations, handgun can randomly headshot, an additional scene with Forest and some change camera angles and textures.

The third version of RE 1 which I believe is only on the American PSN as it was never released outside of America was
Resident Evil Directors Cut Dual Shock
Based on the Directors Cut version.
This version supports Rumble and Analogue controls.
Has a completely reworked soundtrack which is generally considered quite bad and has a really really bizarre story behind it.)