David,
They’re quite similar in a lot of ways (weight, zero drop, minimal cushion, wide toebox). Mostly I’d say the TrailRoc is just a better/higher quality Superior. The TrailRoc’s have a pretty durable upper. After 400-500 miles the front mesh starts coming apart, but pre-treating with seamgrip extends this by several hundred miles.
The Superior might be more resistant to feeling rocks. Even without the rock plate (I’ve never used it), the Superior seemed to insulate from the trail more. Some folks will like this, but I never found the TrailRoc’s to give too much feel. Maybe on super pokey ground it’s not ideal, but for the most part I like the livelier connection to the ground that the TrailRoc seems to have.
The Superior seems to run a bit larger, whereas the TrailRoc’s are more true to size. IIRC, the Superior also lifts you a bit higher off the ground because I think the sole is thicker. The sole also tapers outward to give a wider footprint in the Superior, which I guess might add stability, but might also be a negative in more technical terrain where a wider shoe is a liability.
The rubber on the TrailRoc seems grippier. It’s great. A nice medium aggressive tread so there’s not excess drag, but still enough grip in soft soil. The rubber on the TrailRoc wears at a good rate. It’s pretty worn around 600-800 miles but you can push it much further if you don’t mind it a bit bald. If it wore faster that wouldn’t be good, but if it wore slower they wouldn’t have as good of grip. Overall it feels like a well rounded shoe because the upper and sole wear out at about the same time. I never got to put enough miles on the Superior to see how long the tread lasted, but it seemed (subjectively) less grippy.
Another shoe to check out is the Merrell Bare Access Arc 4. The upper seems extremely similar to the Trail Roc. I’m using them now. After pre-treating with SeamGrip (the open mesh near the front), it seems like the upper will last a good while (at least 500 miles). The sole is less aggressive but a delight on most trails. It has multiple pieces of Vibram rubber tread glued to softer foam. It absorbs rocks really well, while still giving good feel on the trail (kinda like the original GoLite shoes back in the day). Downside is that sliding around on scree/talus/loose trail can cause the sections of tread to start to peel off (this is not the intended use of these shoes). I’ve been pretty hard on mine and the sole is still useable at 500km (300 miles) but probably only has another 150 miles. On good trail (e.g. PCT) the vibram tread might not start to peel, and thus last a good long while. I’ve really been enjoying them and there are some good deals online.