What is the difference between full and system builder 8.1

I see an option to buy either full or system builder for windows 8.1 for my new build so which one do I pick and why? full:
http://www.amazon.com/Microsoft-Windows-8-1-Full-Version/dp/B00EDSI7QO/ref=sr_1_1?ie=UTF8&qid=1417485150&sr=8-1&keywords=windows+8.1
System builder 64bit oem:
http://www.amazon.com/Windows-8-1-System-Builder-64-Bit/dp/B00F3ZN2W0/ref=sr_1_2?ie=UTF8&qid=1417485337&sr=8-2&keywords=windows+8.1
Answer #1
http://www.tomshardware.com/answers/id-1992594/windows-system-builder-oem-full-version.html