The difference from business to first in the Qatar Airways Premium Terminal is that first offers massage chairs, a spa which has a sauna and massage rooms + a bedroom. The range of drinks and food is the same between the two however. You pay extra for massages in the first lounge.

Yet more exclusive is the VIP lounge in the airport. This is the building between the Premium terminal and the normal terminal. It is very nice inside but the key thing it offers is convenience as you only need to turn up just before departure and are taken to the plane in a waiting BMW 7 series :)