I took both the Port Authority and Mizzen & Main shirts on a trip, here are the results of my "field test."
Port Authority: I wore it for a day of travel. It was very comfortable, like wearing a golf shirt only with a dressier appearance. Tails are short enough to wear untucked if that's your thing. Very little wrinkling after a day of planes and airports. Did my typical wash-in-hotel-sink thing, and it dried quickly and looking like new. Wore it on the flights back. Conclusion: Great travel shirt, build quality just OK, good compromise between dressy (sort of), comfortable, and convenient.
Mizzen & Main: At 5x the price of the PA shirt, this solid white shirt looks crisp and dressy. It doesn't look like a knit shirt, it has a very fine weave. It emerged from my suiter with no more wrinkles than it had when I got it at Nordstrom. I wore it for a long day of meetings and here's where it really performed. At the end of the day, it looked no different than at the start - still crisp and ready to go. (My cotton Tyrwhitt shirts start off looking great, but at the end of the day show more wrinkling and look like they've been worn.) Hotel washing of the M&M shirt produced an OK result with some fine wrinkling from the wringing process. Wearable, but I think I'll try a different water extraction process next time. If it didn't get soiled or sweaty, this shirt could go for more than one day without laundering.
And, I got the Wool & Prince shirt. Gorgeous packaging - a nice rigid shipping box, tissue paper lining. The shirt itself looks great, fine for business at any level. I'll report back on that one, I have a few more trips in the offing.