I know Zone is closely related to BDS which is a fantastic company. I talked on the phone to a zone/ bds dealer who claimed they are very similair, I also called zone who claimed the same thing. Essentially zone is the more expensive parts rebranded and sold cheaper. As a matter of fact if you bring the zone 3" kit (in terms of (completeness) up to the level of the BDS kit they almost come out even in terms of price. Which is why i bought the bds instead of the Zone. As far as I am aware they use the same springs and shocks as the BDS which is all that really matters with a 3" lift, the ride is better than stock.
The premium priced kits are nice but at 2.5" of lift its really rather pointless to go that route, Both lifts use mostly stock suspension components anyway. Your not getting any added offroad performance for your money. The only thing you will be paying for is the name, if you were doing a 4" kit I'd definately look into a more premium kit as then you are changing control arms, track bars, brake lines etc etc