They're pretty much the same thing. The RC kit has shock relocators (I don't see why you'd need them with only 2") A spacer lift is a spacer lift so brand doesn't really matter. I'll bet you could find cheaper.
Edit: Looks like the Rusty's kit has shocks included. I'd say find one that includes shocks
2004 4.0L I6 TJ BUILD:
1997 2.4L I4 TJ BUILD: