IFS is better for just about everything you actually want a suspension to do.
Solid is simpler, and for a given level of toughness cheaper, and is easier to adapt to custom installs.
I'm no big expert, but like Firethorn read up on it myself, and that's the gist that I pulled away. Lots of guys using them as part of a custom build.
Both my old Trooper and current 4Runner have IFS. While I'm no big rock crawler, they've certainly taken care of me in the situations I've gotten myself into to date.
The 4Runner has KDSS, which might even partially rely on IFS to do its thing.