A PC version might be coming if only based on how many sources continually listed it as a PC/360/PS3 game. Right now with the 360 vs PS3 version, it is safe to assume the 360 version is better. I have played all three versions of GTA4 quite a bit (vanilla on PS3, episodes on 360, messing around on PC) and the 360 version of GTA4 is a noticeable improvement over the PS3 version, I thought; not just in how it looked, but it seemed to run smoother. The PC version was an even greater improvement over the 360 version. Obviously it would look and run better on improved hardware but the stand out thing for me was that the controls were far more responsive using a 360 controller. I'm getting RDR on the 360 and will double dip on the PC eventually. Skipping over the PS3 step entirely.
Also, consider that GTA3, VC, SA, 4, Episodes, and Bully all came out months after the console versions. Things can always be different, don't get me wrong, but there is some history there. Don't know about the newest Midnight Club game and Table Tennis was 360 only (or on the Wii too...I don't remember)
I'm not too worried about how it will compare to GTA4. I thought the episodes of liberty city were way better than regular GTA4 even just for some minor gameplay improvements (checkpoints? by gad, sir, rockstar are pioneers!) and from what I've read of RDR, it sounds even better.
I'm still wondering exactly how lock on works here. My problem with free aim on the console versions of GTA4 was that the aiming felt more sluggish than Killzone 2, so I used lock on as a crutch. The new lock on sounds like CoD4/MW2 now.