The claims that Tenara will hold up in outdoor use echo the old claims for polyester or nylon thread when that "replaced" plain cotton. And I'd expect the same downside to it.
If the thread is stronger than the material it is used in, it will saw the material and enlarge the thread holes. If it is software
, it will wear out first and need to be resewn. And, unless the thread neatly plugs the holes by some mechanical means, they will leak in the rain.
What used to be recommended was "DaCot" thread, dacron core
with a cotton outer layer. The logic was that the Dacron had durability but the cotton will swell up when it gets wet, to help seal the holes when it rains. To me that logic still works, but even with camping gear
it was never good enough--you have to use a seam sealant
(used to be urethane, now some kind of water-based product) to seal the seams. Which is probably part of the reason GoreTex rainwear comes with seams that are TAPED and sealed after they are sewn. Needle holes are simply going to leak, sooner or later, no matter what you do.
I'd suggest letting the bimini company work with the materials they are used to and familiar with, if they are good folks they will have reasons to be working with those materials. If threads punking out in the sun are a big problem...seam sealant
, UV protectant, or...maybe they can glue some type of "ribbon" over them, to really seal them just like GoreTex rainwear is sealed?