I believe I had about 5K miles on the terra's before I went trails. I swapped the trails at about 24K, so I had about 19K miles on the trails before going to the ridge grapplers.
I haven't put the Ridge Grapplers through heavy mud, so I can't make an assessment of how they stack up against the Trail Grapplers in that regard, but offroad on rocks the Ridges are awesome.
There's kind of a reason why Nitto has basically said, if you ask them in person, that the Ridge essentially kills both the Terra and the Trail product lines. But they're keeping the Terra and Trail because one is a distinct AT tire, and the other is a distinct MT tire. The Ridge however combines the best of both worlds.
If I'm being frank I rolled the dice on the Ridge Grapplers, and both Walt and I were a bit uncertain if it'd pay off. However what we've found is the Ridges are far tamer on the road, work just as good offroad, and have absolutely no hum on road unlike the Trails (the trails are still far quieter than their Toyo Open Country R/T counterparts). I'm actually able to hold a conversation in the 4Runner when using my cell phone unlike with the MTs.
The other thing is I drove back through the Mojave from Vegas to LA, in torrential rain, and you can just feel that the Ridge Grapplers handle wet roads far better than the MTs.
I don't distinctly remember the Terras all that well, but I'd say it'll come down to if you primarily drive on roads with a little offroading maybe go with the Terras, if you do equal parts go Ridges, if you're mostly doing offroad go Trails.
All three are really good, I just think the Ridges are pretty much the best of both worlds without any downsides.