You do realize that Gold on AS/DL is a 50K mileage level*, and Gold on AA is a 25K mileage level, right?

So... what exactly are you expecting out of status? Best chance at complimentary upgrades? Awards? Lounge access on international itineraries? The bottom line is a 25K/50K elite level is no great shakes on any airline- you won't be getting complimentary upgrades on your TPAC/TATL travel. So getting some idea of what you want out of elite status other than "gee, isn't that a nice shiny card" will help us advise you here.

Also... DL will soon be requiring minimum spend to hit DL Gold. At present, AS and AA do not require minimum spend.

One other thing: US has some downsides, but US probably has the best ability for you to get cheap upgrades into their F cabin compared to DL and AA. I wouldn't discount them as a possibility.

*(40K if you fly AS only, which is probably not an option based out of TUS)