I've recently read that the X360 DLC packs for GTA4 compare in size somewhere between VC & SA, so to get the most
out of it, I'd say X360 if you have to pick just one. As I understand, you want one made after Sept. '07 to avoid the
"Red Ring of Death" issue. According to a local game shop, if you look through the grate on the left end (looking at the
front of the console) you'll see a copper strip on the older units. Newer production apparently doesn't have that strip,
this is from a couple of local sources.
Eventually I plan on a PS3 as well, since both have exclusive games that look good.