I have both the PS3 and PC versions of this game and have played the game somewhat on both. Here is why I feel you should definitely purchase only the PS3 version and not the PC version.
Of course the #1 reason is the size of the viewing screen. The game sure looks nicer on a 46" TV than a small monitor.

#2-The chat text from NPCs on the PC monitor is so small it will give you eyestrain to try to read the chat text. On the large TV the chat text is easy to read and more enjoyable.

#3- Clicking on chat text many times with a mouse on the PC version will definitely strain your wrist muscles. With the PS3 you use a PS3 controller and there is no strain at all, just tap a button for constant chat from a NPC.

#4-The graphics on the PS3 version is just as nice on my TV as on my PC version. So you will not be missing out on any visual beauty