um well im pretty sure im one of the few on this website with a scca race license... and have actually roadraced at several tracks, not just chin events or auto x crap. So, yes shocks and springs are cool if you have to run them such as a spec class or a class that does not allow threaded shock bodies aka coilovers. But a proper coilover set up has much more adjustability then a spring shock combo. So you can corner weight and set up for the ultimate suspension rig. Now you can get shocks revalved and different spring rates, but you can also do this with a threaded shock body also.
Now there are coilover sleeves availible in w.e spring rates you please, but unless you shocks are valved for your set up you will destroy you shocks and not have the correct damper and rebound. Also this is not part of the shock body so sag and also sleeve lift will happed under hard cornering, aka drifting.
For drifting, a coilover set up is a must for anyone wanting to be able to adjust to different tracks and or fine tune their suspension set up. But if you just want to lower your car and stiffen it up a bit, a shock combo is for you.