I have fish mostly Lake Michigan Tribs on the Wisconsin shore but I have fished a couple Lake Superior Tribs on the Wis. and U.P. shores. I only have 2 years of doing this under my belt but I fish typical about 60-80 days a year for Steelhead.
If I had to use only one fly it would be a egg pattern. Without doubt I would bet more Steelhead are caught on egg patterns than any other type. I also use beads at times. I am not convinced yet that beads are drastically more effective than yarn eggs. I use both during a season. I have been told by various guides that they definitely out fish yarns eggs by up to 5 times. This would make beads the most effect fly out there. I know all the snobs on their high horses will now comment on beads and that's fine. I don't have a problem with it neither should any other fly fisherman that's interested in learning and increasing his skills.
I have tried sucker spawn, various nymphs, estaz eggs all with very poor results. I am sure some of it is one tends to fish with what has worked in the past the most. I know I do.
If someone wants to narrow their focus when fishing for steelhead to one method or fly that's great. Nothing wrong with that. One time I followed a spawn fisherman with a center pin down a run. He didn't catch a thing. I caught 2 steelhead and a brown after he fished the same spot minutes before me. It was great to watch him just shake his head as I landed each fish. I have watched the centerpinners just nail the fish in early spring in high dirty water while I fished the same water and caught one fish all morning. It was great to get the upper hand for once. It's not that I am a better fisherman, its that I was using a more effective method under the current conditions. The point is every dog has its day. We all set personal limitations on our fishing methods. Even the centerpinners. I will be the first to admit I don't know alot about steelhead and I'm not a very talented fly fisherman. But I do want to learn more and I want to get better. One of the best ways to learn more and improve your skills is to try different methods and flies.
Don't be afraid to try something new or different. Start with what has worked for you in the past. Talk to other fisherman, even the centerpinners, sometimes they use artificial lures under their bobbers. If you can't learn from others than your not listening. Most fisherman I have talked to are very open with what they are using and with thier experiences. Also talk to the guys in the local fly shops. I personally have learned a ton from these guys. They were great in getting me started.