Ditto on the extra internal room...
I like the preceived (may not be larger than the 200 but it sure seems so when laying inside) internal room that the 250 gives. I feels like I'm laying inside one of my small packpacking ground tents. I got the 250 for the extra head & foot room (could have gone with the 150) because I wanted the option of bringing my pack inside if needed. The extra foot of length also helps you lay flatter is you want.