I am in the same exact boat as Hunter 79. From my research, I would echo the responses above in that BDS is a premier lift and Zone comes from the same parent. However, the BDS kit comes with skid plates and warranty, and replaces the struts where the Zone uses the stock struts and spacers. Either of BDS 4 or 6" kit will accept 35's and Zone states that 35's are "tight, may require trim" with the 4" lift. I think the owner has to evaluate how important mileage or performance is with either kit. With a lifted vehicle, both will suffer for numerous reasons. 35's weigh more and is more rotational impact than 33's, but for me, it is about balancing "the look" (4/33 or 6/35). Some 35's on 4 inch lifts look stuffed and 33's on a 6" lift look lost. You can re gear, but that is expensive. The speedo will be off by about 4-5 MPH but it does add up extra mileage on the odometer. You can recalibrate with a hand tuner, but it will show on the ECU and could void warranty.
I have driven a Pro Comp 6"/35" and I didn't think it was too bad (5.3L with 3.42), but it was a 13-15 MPG vehicle (real world). I can live with that, but not 8-10 MPG. I also drove a 4"/35" Pro Comp Rocky Ridge at the dealer and thought it was fine too. New technologies have really changed the ride quality with lifted vehicles.
I was not aware that the BDS coil over set up were adjustable 4-7". I would like to know more about that, as I would like to have some rake too. 5" in front and 6" in rear sounds ideal to me. Not sure if rear springs are needed over blocks. I do tow ATV and sleds, so I don't want a lot of squat. I am definitely in for BDS, just not sure what version to pull the trigger on, and plan to keep the stock 20's in any case. With 20's the 35's would offer more cushion for the sidewall of tire which would help ride. I would like to see more side by side pictures if anyone has some.