There's a huge difference between 1920x1200 w/16AA and 720P w/2x or the fake AA of the PS3 version. Also, the PC version loads way faster than the console versions and plays with either a Dual Shock 2 or 360 controller.
I'm not suggesting that there isn't a difference. I suppose it comes down to what one considers a "major difference". When I think major difference, I'm thinking about the rifts we saw last generation between PC and consoles. Half-Life 2 on the PC version versus Half-Life 2 on XBOX, for instance. Or, if limited to consoles, Resident Evil 4 GC versus PS2. The differences there are massive.
Of the points you've made, only image quality really means anything and whether it matters depends on the display you are using. If you are using an LCD with 1920x1200 native resolution then, yes, the PC version will look MUCH cleaner as 1280x720 tends to look pretty nasty on such LCDs. As you are using such a display, it probably does make a larger difference. I either use a Pioneer 5080 plasma (1366x768 display) or an NEC trinitron CRT monitor (which produces awesome results at all resolutions), so using such a resolution isn't necessary. Though, I was surprised that the game had no trouble running at 60 fps in 1080p mode (my TV accepts 1080p and downscales it, so I could still try it out).
I didn't really detect a massive difference in loading, though. The PS3 version seems to load just as fast as the PC version (which is to say, there is no loading between most rooms and when the "Now Loading" text DOES appear, it disappears within 3-4 seconds. There is a much larger difference between the PS3 and 360 versions (in terms of loading time) than the PC and PS3 versions.
As for controller, well, the PS3 controller is pretty much the same as a Dual Shock 2 and that is pretty much the only way to play. The 360 pad sucks for this game.
Again, I'm not suggesting that the PC version ISN'T the superior version, I just find it odd that people are pushing it as if it is a massive leap. There are TONS of other examples of console ports that ARE VASTLY superior to the original versions, but this isn't one of those cases. The PC version basically buys you improved image quality and a couple features. Compare this to, say, Mass Effect where the PC version runs at a rock solid 60 fps, loads extremely fast, and no longer suffers from texture pop-ups. THAT is a big improvement over the original.
You ARE running this with v-sync, though, right? I recall someone bragging about their framerates going above 60 fps with v-sync disabled which produces inferior image quality compared to a locked 60 fps. They were only interested in the higher number despite the fact that it looked worse due to tearing.
