I don't think GTA IV will be 'make or break' at this time. It will sell well for both (in proportion to install base) but I don't see it changing the landscape - it would need to be exclusive IMHO to do that. The real battle this year I think will be MGS, etc. on PS3 with GOW2 and Fable 2 etc. on 360.
I just don't think enough average joes are going to even know DLC exists.
Try to be reasonable... its easier than you think...







