Well, I would say the full show badge simply because it says pre-registered, meaning you don't have to wait in a super long line AND you can ensure your spot for Nats.
If the other one also lets you do the same thing it is up to you BUT most people get in on Friday and you can take care of your badge and stuff that day AND get some last minute playtesting inside the playing area, where a lot of people will prolly be.