Interesting points and discussion even though the thread drifted into an IRS v. solid-axle debate. I grew up in Mississippi with plenty of rain and mud. We learned how to drive 2WD off road. There was usually a tractor nearby if we got stuck. The 4WD vehicles sat all year until deer hunting season opened in the swampy woods. When I bought my 4Runner in '04 I went with 2WD because I wasn't heavily into "off-roading" mostly just very backwoods Sierra forest roads. It worked out fine.
However the rest of the USA isn't necessarily like a muddy road in Mississippi. I owned a Jeep CJ-8 for many years and the point is taken that having 4WD can save you a lot of grief and often a tow. I think pulling a 16000# 5'er I will opt for 4WD.
Thanks to all who have replied.