I use nylon clevises on all my combat planes. They go plenty fast, and the nylon handles it just fine. Nylon won't strip if put on properly (watch that metric vs english thing). Properly installed metal clevises are a bit stronger, but as others have said, they can fail as well.

If you use metal, your best bet is to use a jam nut on there. You DO NOT want the clevis rotating in flight, any movement will result in wear that will lead to it stripping out eventually. So locktite would be ok, but you'd loose the adjustability, which is why people use jamb nuts instead. You also don't want any movement on the nylon either.

IMPORTANT: When putting any clevis on there, make sure at least 2 turns of threads are sticking out between the clevis arms. Threading the clevis only part way on the rod is asking for failure, no matter what material. At the very least, be flush. Sure, you get get away with less, but you aren't getting the full strength of the clevis and are risking failure.

btw, control systems are one of those religious things that you will find people swearing up down and sideways that their way is the only one true way and all the rest are doomed. I'm a bit agnostic.

Instead, I suggest you find what you are comfortable with and stick with it. I always use the same brand nylon clevises on the same metal rods, done the same way. I know from lots of experience that they are a good fit together and won't fail me. You won't find me buying another brand rod or clevis, not because they aren't as good, but because I won't know until I get it that it will work just right. It doesn't take much in the way of under- or over-sizeing to make stuff not quite fit right and lead to problems. (notice I didn't mention what brands I use? It's because they aren't any better or worse than the others, just what I'm used to).