leaf vs coil rear suspensions 67 - 72

[1969K10]

So, been driving the g/f's '68 C10 w/ coil springs. I've only ever owned/driven leaf spring rear end vehicles. It seams to me that her coil rear is exceptionaly willing to spin tires. Got caught in a killer rain storm yesterday, and going up a hill, the back tires picked up and started spinning. I really don't think that would have happened in my leaf sprung rear ends. Anyone got anything that would help me understand why? the rear end of her coil truck was supposedly all replaced about 1-2 years before she got it ~18-24months ago, so it's not old and mushy. I also seems really willing to let loose in corners when I know my leaf springs don't.

THX