Depends what you are fishing for, and what the water is like, AND what river it is.
Coho I generally do better with spinners under all conditions. I can do equally as well with spoons some days, but coho don't seem to like a single action on the spoon (ex cast and retrieve). I like to jig the spoons back in to get more action on them and it works wonders.
If you're fishing the vedder, stick with spoons. R&B silver/brass 50/50 spoons and gold hammered crocs if the water is low and clear will be all you need. I have caught very few coho on spinners in there for some reason, and I have given both equal effort. Spoons out fish spinners probably 10 to 1 for me no matter what I have tried.
Honestly, there is no definitive answer for your question, as I said, it all depends on species, the specific river, and water being fished. I have learned a heck of a lot sight fishing the past 2 years on the island, figuring out what jigging methods work, and what gets coho to bite under different circumstances. My advice is don't just stick to one thing, if you want to pack light, take a spinning rod with spinners, spoons and jigs. If you don't get a hit in the first 5 casts and you know there are fish there, switch up to something different or a different method. If they are going to bite, coho bite fast.
Steelhead are another story, they are all about spoons, summer or winter run fish, on any system I've been on. They like the wobble. They like spoons on the swing or a slow cast retrieve. They will occasionally go for a jigged spoon too, especially if they have been flogged and are gun shy a little bit. Winter run fish will hit metal like crazy despite what most people will tell you...