I also got offers from both and chose Mesaba. Starting in May and am upgrading this spring. I am an upper midwest guy though so an MSP base did it for me. We are still growing and have great people who are generally happy (getting some provisions back after bankruptcy) and the flow through has started. However, as noted before, if you are coming in now the instabilty of the industry as a whole means don't count on upgrades/flowthrough or anything a year from now.
I would say go with QOL--whatever that means to you.