It seems like JAL flies their SkySuite (the Apex Suite) to/from DFW, so I'd take JAL in a heartbeat. JAL's regional J seat, that sometimes flies to less popular west coast cities, leaves quite a bit to be desired but the SkySuite is fantastic. If you were looking at the herringbone seat or a 767, I'd take AA.

Aside from the seat, the soft product can be quite different. JAL is quite good with refills, and food is easy to order between meals using your IFE. JAL and AA share some catering on some routes, but ultimately the crew is still responsible for "firing" your plate. I've never had a steak cooked past medium on JAL, if that sort of thing matters to you.

I love a warm cabin, but FWIW my wife is more like you and would happily sleep in Siberia without a blanket. She found the longhaul flights manageable with a USB-powered fan, but the regional J too warm to sleep. If you're taking day flights on the regional, I wouldn't overthink the long-haul and go with JAL.