You could check out the Swobo Folsom at swobo.com. Many of the fixed geared bikes come with flip-flop rear hubs, they can take fixed or free wheel. Specialized Langsters, Giant Bowerys are like this. Though the Treks are fine.

Take one more afternoon, ride those two treks, find a store that has another option like the specialized langster or giant bowery (I wouldn't be stuck on those brands, it's just that they are very commonly available), ride those. Then buy the one that feels best.
Everyday you ponder is one less day you're riding.

Also one of those Treks (3.0) is a 7-speed internal hub, I'm sure its fine, but would cost more than the single speed.