R – Is it better to use Nested Master pages or User Controls for multi-sectioned website

I am creating a website that has 5 different sub-sites each with the same overall look, but each has a different logo and added navigation.

What do you feel is a better approach:

• Use the new nested master page capabilities to create 5 sub-master pages.
• Use a single master page and dynamically load user controls corresponding to each sub-site's
  specific logo/navigation.

I'm currently going down the nested master page route.

Update (12/19/2008):

I am using Nested Master pages, and it is working out great. You are able to pass-through ContentPlaceHolders, and even have default content for the placeholders.