This is true if you're only looking at MySpace and Facebook.
If you go back a decade, MySpace won the social network space because you had a lot of control over the webspace. Because setting up shop was more about expressing your personality online than about showing off your vacation pictures.
> (I am not a UI/UX guy, take my thoughts with a grain of salt).
Your thoughts are actually absolutely correct as long as you're not talking about social network sites. This is common wisdom in Information Architecture / User Experience. Which isn't surprising, since they wouldn't have a job otherwise.
In my view, this is the differentiating factor between MySpace and Facebook. On MySpace you have a lot of control over the webspace -- and it's horrible and atrocious for the visitor to the page 99% of the time.
Facebook makes the layout standard, and this benefits visitors to pages because people can find the information they're looking for.
(I am not a UI/UX guy, take my thoughts with a grain of salt).