According to VgChartz:
GTA IV
360 9.87
PS3: 9.38

There are also stand-alone DLC content so I guess you can count that too.

Episodes From Liberty City(6-month timed-exclusive on Xbox 360)
360: 1.99
PS3: 1.44

Here's an example of how a Rockstar Games game can sell when no platform is shown preference.

Red Dead Redemption:
360: 5.09m
PS3: 5.02m

Undead Nightmare(Standalon expansion/dlc)
360:0.88
PS3: 0.95

Main game + DLC combined:
360: 5.97m
PS3: 5.97m

Look at that! It's a tie! An extremely successful new IP without any timed-exclusive content for any platform. No one gets screwed over here, everyone is happy. Take notes Activison/EA.

i don't think so honestly.

Off the bat, I think the 360 version will outsell the PS3 version. However, lifetime-wise, the PS3 version will come out on top.

sounds very feasible. will initially seel more on xbox 360 then be overtaken after about 9 months on ps3

It'll be nearly 50/50, with the 360 version selling more at launch but the PS3 version surpassing it later.

no reason it shouldnt. GTA IV had an equal split between both platforms and that was when the 360 was alot more popular than ps3 and had exclusive dlc. in 2008 ps3 and sony were having a torrid time.

http://spong.com/article/17386/GTA-IV-Sales-Split-50-50-over-Xbox-and-PS3

I could see it happening.

These numbers won't mean anything until early next year. When you have AC III, Halo 4, BO 2, and Christmas a lot of people won't start flocking to pre order a game that still doesn't have an exact release date. Once they announce collectors editions, a real release date, and if there is exclusive DLC that is when you will see numbers jump a certain direction.

Could go either way, I'm expecting it to end up 51/49 or 52/48 for either console. so it will be a negligible difference between the two.