Beyond the obvious, that the NSF Fellowship Personal Statement is "Why am I good for the NSF," and the Academic Statement of Purpose on a graduate school application is "Why grad school and why grad school?", how different or similar are the two essays?
Having already written an NSF Fellowship application, I'm now in the process of writing my Academic Statement of Purpose for grad school applications, and I'm trying to figure out how similar these statements are going to end up being.