Wirelessly posted (BlackBerry9630/4.7.1.40 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/105)

Depends on what you like, I suppose. I don't mind the CO seats and I find the curve of the UA seats a bit "off" for my tastes. I know I'm rather abnormal in many ways and I'm sure this is just one of them, but it is very much a YMMV situation.

As for why they are different, the airlines spec the seats and source them from different suppliers. Lots of options out there.