[dsheth]

I think the main difference is that Centos strives to be "100% binary compatible." We write software targeted to enterprise users that are generally running Redhat. Our development and test platforms are Centos.

Scientific Linux, while compiled from Redhat sources, does not strive for binary compatibility with Redhat.

[rdtsc]

They compile the same SRPMS after they strip the logos and Redhat references out. Yes, they add extra optional packages like OpenAFS and others, but you can just disable those repos.