I run a 4" SUA in my YJ, and we do mostly mud; never had an obstacle I could not conquer as a result of lack of articulation... (there have been many that have beaten me, but not for that particular reason!)
I think your best bet for mud is 4" lift and use the rest of the money you would have spent on a SOA for lockers... Now THOSE make a difference in mud! I have actually outwheeled rigs with more power (I have the 4 banger) and bigger tires as a result of better traction coming from the lockers.