Hi Alex, this is a "road" suspension set up. There will be others for drag, circuit and drift, they will be more tailored to the activity. I will be doing the engineering on them progressively over the next month or so.
The adjustable stabiliser bars mean you can have a high grip road car and a low rear grip drift car. All you do is select the large rear stabiliser bar (24mm) and change the bar settings, firm for road and really really firm for drift. If you have ever driven a drift car on the road in the wet you will know how important that ease of adjustment is.
As for a comparison with a simple set of springs and shocks, well there isn't any. You would have to have 2 sets of rear springs and swap them over, soft for road and hard for drift. In addition you wouldn't get the camber and caster adjustment (both essential in a road and drift car) that this kit offers.
Lowering and raising at will, is truly a bit of a wank. After the novelty wears off 99% of people don't bother. Plus, on a Skyline, it changes the suspension geometry so you would need to do a wheel alignment everytime you rasied or lowerd the car. Plus resetting the corner weights would be a good idea. That's what we do with the race cars every time. The reality is you won't change anything but the look by raising or lowering, the effect on handling on a double wishbone suspension is mostly because of the wheel alignment changes, not the height itself.
The bottom line, if you are going to drive the car mostly on the road and do a little drifting ocassionally then this set up will do the job. If you are going to do a lot of drifting and only drive the car on the road to and from drift events, then I would hang out for a couple of weeks until the drift kit is available. It will also have the alignment bushes and settings for that application.
Hope that answered your questions
cheers