Need help selecting an airline for work
 

I hope I posted in the appropriate forum, as this isn't targeted at one airline.

I am looking for the best airline to use for business. I have a sales territory that runs from ME to FL incl AL and WV. Basically the Eastern US. I typically fly out on Sun PM or Mon AM from TPA and home on Thr Night for Fri afternoon. My company prefers that I keep the cost under $400 r/t if possible. I typically book flights that are less than 2 weeks out, which I am working on trying to plan further in advance.

I have spend the past 6 months on US Airways and hit Gold status, but haven't been happy with the service

Anyone out there have a recommendation on a better airline for the East Coast?

I thought about delta, but I heard that TPA has about the highest concentration of medallion members, which makes the upgrades difficult. I normally get upgraded on USAir on at least one leg of my trips.