A full spool eliminates the entire differential. It is basically a solid piece with two holes for the axles and a big ring that the ring gear bolts to.
A mini-spool is added to a factory differential to remove the spider gear and make it act like a spool. But it isn't. It is still a factory differential, just with a couple parts added and a couple taken away.
No idea about the drag world (I am here reading everything so I can learn), but in the circle track world, a mini-spool is dirt only. The dirt will give before the mini-spool does. Asphalt, full spool is the way to go. With more grip, a mini-spool will frag quickly. Granted, they are turning a lot, and turning under power, but I wouldn't run a mini-spool on anything I was putting big power to asphalt.
Actually, I am running a full spool and all I have is mild 306 in a 2500 lbs car.
V8Mongrel.com - updated August 21