I have noticed that many top guides still use mono and backing and check and replace it frequently. I am still a mono guy for salmon. I don’t guide and in terms of skill consider myself in the middle skill range and can still hold my own with single action reels but I am getting old so backing and full length mono stretch adds a safety factor for my increasingly slower reflexes and I am dreading the day when my younger fishing buddies may start suggesting a lever action reel and tell me to keep cranking. I have seen a lot of anglers who can blow the doors off me playing big fish on single actions, especially the younger guys with lots of fly fishing reel experience on big fish.
Braid is thinner at higher lb test and super strong when new and undamaged on higher end very top flexible rods with a good top shot of mono on the reel for stretch on rods that don’t have wear groves in the eyes to slowly wear or partially cut it. It can also cut or partially cut more easily on things like trim tabs than mono will nick or cut. It can also get very weak with wear and damage and it is more difficult to notice wear and damage compared to mono. Further it is far more expensive and usually of higher pound test so some assume, incorrectly, that it will last forever and not break even if degraded with use and be less inclined to swap it out. Braid knots also need to be retied frequently and good working easy spinning swivels are perhaps more important than with mono. I have noticed that braid fished for salmon will sometimes tend to develop a permanent twist especially if fished with a flasher.
I do keep one moderately stiff tipped rod with a reel loaded with braid with a very short Mono top shot to the flasher. Why do that? - Because if you are, or are out with reasonably good experienced single action reel fishermen who know how to read the fight and get on and off the reel palming and reeling position very quickly to minimize pulling the hook out of the salmons mouth, it can add to the fun and interest in playing small salmon.
The braid like steel does not stretch much if at all and tends to transfers and magnifies every twitch, head shake, change of direction, jump, roll and pull, making fighting small salmon seem like you are playing a larger salmon on a single action. Even then you will pull more hooks, but who cares. When you are out looking to catch large Chinook and all there are around all day is 3 to 7lbers of any salmon species, we sometimes throw down the somewhat stiff braid rod with the drag set low to up the fun factor and I also think it helps sharpen your skills on the single action reels.
Of course if you do luck into a 40lber on this setup, you better be fast adjusting the drag for more resistance and reading the fight and getting on and off the reel handles and palm position fast when it decides to run. In my opinion you will have some well justified increased bragging rights if you do manage to get that big Tyee in the net on a stiffer heavier tip rod with full or near full braid with a short mono top shot up to the reel.