Since I've been really open and honest in my thinking, and have talked about the Raptor...A LOT...I'll share my thought process on why I'm switching.
Ultimately it comes down to capabilities out of the box.
If you think of it like a big venn diagram, the 4Runner and Raptor were heavily overlapped, but the Raptor has twice the power, a ton more features, factory long travel, 35" tires by default, and it was actually cheaper to insure it overall.
Frankly even though there was that overlap, the 4Runner was 1000lbs heavier, half as powerful, way lacking on features I wanted, and the crux of the issue...it was more aftermarket than OEM. I spent most of my time just keeping creaking noises, squeaks, etc, from happening in an effort to keep parts playing nice with each-other.
I really enjoyed the 4Runner, and on technical terrain it would haul ass over obstacles that the Raptor had to work harder on. That said, I didn't find the 4Runner a very enjoyable vehicle to drive other than that. I also rounded out at about 12.4mpg. I'll get 18mpg on the raptor, with a 36gallon tank for long distance trips.
Baja has become something I want to do more of, and not worrying about WHAT I have to strip out of the 4runner just to minimize damage was something I was getting tired of having to contemplate. It cost me almost 10-14K just to repair it after last year's trail of missions.
The 4Runner *is* a good platform, but it needs upgrades from Toyota that I just don't think are coming for a long long time. It had reached a point where I sat there realizing that I wasn't going to solve those problems.
Frankly...I just wanted something out of the box that could do what MY 4Runner does but with way less effort to do so.