A little different set up, but my wall tent is a 12x12 spike tent from MT Canvas. 144 sq feet gives us a very good amount of room for two people, cots, night stand table, small eating table, stove, some indoor firewood, and gear. Vestibule over the front holds the rest of the woodpile and other gear we want to keep dry.
Adding a third person to the mix takes away our table between the cots, all the wood goes outside, as does much of the gear. I really like the single center pole design, but its pretty tight when we try to house three of us inside.
In the end, unless your going to be packing it a lot, I would err on going with the larger size of the two choices.