FWIW, out of all the steel frames I've had, an Anchor made out of Kaisei 8630 was no doubt the nicest riding. Now, that could be the geometry, the bike fit, the actual tubing, the worksmanship, the other components on the build, or a combination of all four; take it with a grain of salt.

With that said, old Italian and modern keirin frames both have the "coolness" factor with their respective enthusiasts, but if you really wanted the best steel and ride quality, you'd go custom.