Lets muddy the water even more here before setting things straight... there are (currently) 5 main options.
- BDS suspension
- Zone body
- MarkMC suspension
- SuspensionMaxx suspension
- Rough Country suspension
- Ready-Lift suspension
- (soon to come - coilovers?
)
The Zone body lift is the odd ball, as it merely lifts the body in relation to the frame. Good to help fit big tires, but does not help attain underbody clearance.
The MarkMC and the SMaxx kits are essentially identical. They are competing companies, however MarkMC is a vendor here, while Smaxx seems to keep their distance. These kits are the 'budget' end of things. While they produce the highest lift of the options, it also uses the stock upper shock mounting method. The stock upper shock mount can notoriously fail if you wheel hard, carry a heavy front-end load (winch, bumper, etc), or drive a lot off road. That is the system's weak point. The system is composed of two pucks... one goes within the shock, to add lift while not extending the max suspension droop, one goes outside of the shock to add further lift, and allow the suspension to extend a bit further.
The BDS suspension completely gets rid of the upper shock mounting method and provides a single lifting component made of powdercoated steel. This block lifts the spring, and also readjusts the upper shock mounting point to provide a bit more downward articulation. It provides improved shock mount bushings that resists the wear and tear of heavy duty use.
The Rough country is essentially a copy of the BDS kit, however it seems to be made of lighter-gague metal. It utilizes an improved upper-shock mount also.
The Ready Lift is a bolt-on unit, and does not require taking the strut apart. The lift is added completely outside the strut, thus lifting the vehicle at rest, but also adding that full amount to the downward articulation of the suspension, potentially putting it into a bind-up scenario. We need more results from this to make conjectures, as only one known member here has tried it so far (for only a few weeks).
So essentially, if you plan to hit extended trails, or rough trails, or plan to add weight up front... go with the BDS. Otherwise, the Smaxx/MarkMC will do fine for you. If you get a wild hair, try the Rough Country or Ready Lift... neither has been fully adopted or put through their paces yet.