For me, the biggest advantage was increased driveshaft length and thus, decreased driveshaft angles. My vehicle has a very short wheelbase and after lifting it, the driveshaft angle became too severe at maximum extension of the suspension. Going with a SYE on the NP231 allowed me to have a longer driveshaft. I also opted for a CV shaft instead of a conventional one for extra strength (reduces angles on u-joints).
However, if you're inquiring about SYE for a transfer case on a long-wheelbase vehicle, a few inches of driveshaft length might not benefit you so you'll have to look at the other benefits to see if they are of value to you and your particular situation.
Maybe somebody else can chime in on this, but I'd guess that longer driveshafts actually travel less distance on the t-case output of a slip shaft. I mean, a long driveshaft does not move as much in the coupling as a short one would. If this is the case, are problems such as dropping the driveline or shortening the spline contact area less of an issue/probability?
Disclaimer: I'm not pretending to be an expert -- this is just what I've gathered from research and discussions with experts...
