Price being equal, would you rather have:
a) Economy class window seat on left side of the AUS-DTW fight or
b) First class aisle seat on left side of the DFW-DTW flight (with the eternal hope that a window seat opens up before takeoff).

I’m a bit surprised how quickly First sold out on these two flights. Having flown business on United’s inaugural SFO-BNE, I know how well they treat J pax for special flights (private lounge area/food/events prior to flight, extra/flight specific amenities on board).
I wouldn’t expect the same treatment here, but at least for the DFW flight, first class aisle seats (that were singles, not pairs, I watched them as they got scooped up) sold out while there were still available window seats in economy.