Coil springs are often touted as giving a smoother ride (not a feature for which I buy a heavy duty pickup). The new Ram 2500s can have as little as 2,2010 lbs. payload rating depending on configuration according to the Ram web site. I would guess that coil springs have something to do with that. The 3/4 offerings from "the other two" usually have around 3,000 lbs. payload. I don't know what state you live it, but it cost me only slightly more to register our 1-ton DRW in Texas than it did our similarly valued (one year newer than our 1-ton) 2500HD. Insurance went up about 10 - 15%, though.
Rob