upper class on expedia

I am looking at upper class fares on expedia and I just wanted to check something. Do I put business class in the search? It still says business and not upper class when I look at the flight details.
Also does it make any difference if I book as Delta flights as the internal flight says First with the delta one and economy/coach with Virgin.
Thanks

Yes Upper = Business Class.

as above, UC == business

depends on the aircraft/route, but DL 'first' on internal flights is more like BA club in europe, you get some more space/service/priority, it's nothing like proper first on an international flight

i've used DL 'comfort' on internal shorthaul and also economy on the same route, and had identical experience, though with 'comfort' i think i got to board a bit earlier which can be vital for locker space and seats were nearer the door