Loads of difference. Short answer: SP is an incredible adaptable container that do can more or less anything. Blueprint is a really good “simple” content container that gives you the most basic features of SP.
The xperts will be along soon to tell you I’m wrong and explain things in more depth :-)
FWIW I use BP by default as a content container, where I want to control things like margin and padding at breakpoints, backgrounds and the best feature of all “pull-up” the content. I switch to SP if I want to do something a bit more advanced, like video backgrounds, align content, size content to screen size etc.
BP and it’s sidekick Sidebar are (IMO) an absolute must for any RW user. Collectively they are leaps and bounds over any other container stack. If I need more than two columns and I don’t want to go down the Sidebar within a Sidebar route I use @doobox Reflow which (again, IMO) is about the best column stack out there.
One thing to add: And I only realised this recently after @Marten kindly worked on a project file for me: Most SP child stacks and lots of the Section Pro stacks (Box, Fix, etc.) work in BP. I’m pretty sure @tav has told me this a hundred times, but it never sunk in until I saw it in action in the project that Marten worked on for me.