im debating the same here
or even going with kirkland hybrid carryon so i can roll it sideways through the isle on the plane

so far for 2 wheels, U121CXW is the only one ive seen that fits exactly the dimensions dictated by DL, UA, AA

but having to gate check it on a CRJ or EMB would turn me off...
still debating here too

these airlines make it so hard to travel...