Both of the 4 inch lift kits on the market maintain the factory geometry, or pretty damn close to it. Definately better then a spacer lift. On any vehicle no matter how much lift you have, the only thing that brings up the ground clearance under the axles is bigger tires. Unless you have portal axles, high clearance axles or Atomic axles....etc. So basically the more lift you have, the bigger the tire you can fit which increases axle clearance. To me, the clearance under the belly is more important. With a good spotter you can negotiate rough terrain with minimal axles clearance as long as you have the belly clearance.