you could get lots of opinions on this, not just from personal preference, but also fishing platform (bank, tiny boat, small boat, bigger boat...).
because I fish mostly from a kayak, I use one-piece 7' rods. I believe that these give me the best control when the fish is at the boat. close combat with a big salmon when you are sitting (or kneeling) at water level gets exciting real fast and things can go all pear shaped real quick.
For coho, I'm looking for a M rod rated for 8-12# leader, that's all I use at Siltcoos. I also use those rods for chinook but usually go up to a MH 12-25# line rod for big fall chinook. IM-8 and HM54 rods have been very good to me.
because our old PB is low to the water, with low sides, I find the 7' rods are just fine for it, especially for people with less fishing experience, but I've also had people join me and use their favorite 8 1/2' to 9 1/2' salmon rods on our PB with good success.
cheers, roger