Did we forget Champion?
Anyway, Miyata did "splined" tubesets, where they insert diagonal splines reinforcing the tubes from the inside, and supposedly allowing them to thin the walls down more and make the tubeset lighter.
Standard 4130 Chro moly double butted tubing is pretty darn good too. Not sure if there's a company that makes most of it. I know it was used in airplanes.
I think every tubeset has a purpose. As long as they're roughly equivalent in weight, and equally unlikely to fail, hard to make a case there's a huge difference between any two nice tubesets.
Here's an interesting discussion in that vein from a
rec.bicycles.tech posting by
Andrew Muzi, via sheldonbrown.com:
I am intimately familiar with Ishiwata and their products, having been in the factory a few times, spec'd many bikes with their steel and built with it. I still use Ishiwata tube for frame repair.
The material [022] is virtually identical to Columbus SP/SL/SLX. The top range of tubes were seamles double butted and the finish quality [as delivered to the builder] was much higher than Columbus. The tubing gauge of the 022 is 0.9/0.6 mm, exactly the same as Columbus SP. It's called "022" because the frame tube set weighs 2.2 kilos. The same material drawn thinner to 0.8/0.5 mm is called "019" because it weighs 1.9 kilos, just like Columbus SL. Many builders, then and now, mix gauges so a small frame might be all 019 but a 56 would have 022 chainstays and downtube for example.
Trek in the late '70s built three racing frames, one with Ishiwata, one Reynolds 531 and one Columbus. Geometry and weight were identical. The prices were unreasonably different because of the cachet of Italian tubing, making the Ishiwata frame the best value. Marketing took over later as the Ishiwata was dropped completely. With the advent of aluminum, the currency crash and the Japanese depression, Ishiwata closed the doors in the early '90s.