There is no indication that the PS3 won't get any DLC, just that the 360 willhave some content that the PS3 will not.

I would think, and this is pure speculation, that because of PS3's surging sales in the US, PS3's dominance in Europe and Japan, the fact that the series is generally associated with the Playststion brand and the fact that it will be a pack in for Europe...well, I don't think R* would leave all that money on the table by not giving PS3 any downloadable content at all.

I own both as well and I'll get the PS3 version since it's technically superior. If the 360 DLC ends up being amazing, I can always trade my PS3 copy in for a used 360 copy.