when faced with the same choice
I went with the simplicty of a Posi 2x, it's better on gas and there is no expensive transfer case to maintain or take power from the primary job of towing
so far in 10yrs I have only broke traction once, and that was a very bad day at site 6 for everyone
the biggest boat I have pulled out was a Advantage Party Cat, not exactly a monster but darn heavy
and after 10yrs I would make exactly the same choice again.. it has worked very well for me