If price/layovers/timing are similar, I would go with Austrian.
The others aren't bad, but the DO&CO catering on Austrian is amazing. Service was great. Chef onboard prepares the meals. Seats are innovative and many of them are arranged so you don't have to climb over anyone. Oh, plus 10 varieties of gourmet coffee drinks.
Swiss and their seats would be my second choice if you don't want to have to climb over anyone.