Hi Flybywire,
I agree with you that the choice of uniform isn't the *only* reason to work for one airline rather than another, though I think it's a factor.
Personally I could never work for an airline where trousers were mandatory and I would prefer not to work for one where they're optional because a) it's not really a uniform, if people are dressed differently and b) even though I wouldn't be wearing them, some of my colleagues probably would, and IMHO that would lower the prestige of the job and the respect shown by pax.
I don't agree with you that trousers prevent colds. For years I used to fly in to JFK, where it can easily be -10 in the winter and with an icy wind coming in off the Atlantic. Working for VS at the time I was in a skirt, shorter I believe than today's style, with 10 denier (or was it 15? I can't remember...) barely black hosiery (normally stockings, not tights).
OK, sometimes my legs were a bit chilly, but I can't say I got a cold once from it, because I was always careful to wear my hat and coat outside of the aircraft.