Know-How Exchange : Branding

Hi...i'm still working on that sub-brands study of mine. just wondered what you think about it. In the travel/transportation industry: does it make sense to brand 'vertically'? e.g. not only normal vs. premium services, but also differenciate premium services, since amenities may vary from region to region. or should we call it all premium/first/deluxe (whatever...), even though they aren't exactly the same. and should a service brand describe the level of service offered(cognitive relation), for e.g. first class=first=the best??
i have so many questions and the issue is so complex. anyway, i'm grateful for any help. thank you.