OK from a Southern Hemisphere liver I am 100 percent with Squilliam where Xbox 360 is exceedingly smoother on the 360. When I was playing Modern Warfare 2 with my brother in Law on my PS3, when a single american, sometimes english man ie anyone not from Australia/New Zealand/ Asia (to an extent) they got shot till they left.
Not because we didnt like them but it killed the speed of the server. And if that person then got the Server (which pisses me off about COD games) we all had to quit and join a different game. Same lag was experience on Little Big Planet.
In Xbox 360 land I decided to play multiplayer on Gears of War 2. Now I was testing out hoard and 3 americans joined in, and i was thinking here we go and it ran so smooth it was insane. (I was a late night player because of being full-time). In fact most of the people I have on my Xbox friends list are people from North America/Europe/UK. Because its smooth... and when I play. I have had the same experience with Crackdown 2, Transformers Demo, Spec Ops beta, Cod WAW I could continue.
Smoothness is different for other people but people in the Southern Hemisphere (OCEANIA AREA) we need Xbox servers. PSN is not nearly up to that standard in the Australian region. And if you think it is internet speed I ran 30mbps Cable internet from Telstra (people from Australia dont like to admit it but it is the most realiable ISP down here) and it was doing it in PSN. The lagginess. It has always pissed me off. One of the reasons why I dont like the PS3 is because of that reason.
That right there is worth the purchase price alone.
Plus there are 20mil independent Subscribers to Gold, there is a bloody good reason for it. And what Squil probably meant by demos is gold users get some exlusively first, as well as other features that are on the xbox.