The first thing I'll say is that frame material is not nearly as important as frame purpose, i.e. what was the frame built to do? So there are flexy steel frames that don't put power down and uber stiff steel frames that will beat you up. Same with any material.

That said, each frame material, when optimized for endurance riding, IMO has different characteristics. Carbon endurance is currently the best compromise between stiffness and comfort, followed by ti, followed by steel. Some local rando riders went through a ti phase on their way from steel to carbon.

Looking at carbon, Volagi has some local followers. Ragsdale rode Volagi on his way to being first American to finish last year's RAAM. They come stock with discs. Willier has a reputation of being a very smooth bike. Thinking about the above rather funny post, I did a local pass ride, which had sections of chipseal interspersed with smooth asphalt, with a friend who was demoing a Willier. I was on older carbon, we both were riding 23mm. He said he was unable to notice the difference between the smooth stuff and the chipseal. I sure could. Progress is.

In more mass market bike, the Domane and Roubaix get good marks.

If you want really wide tires, a Norco Search will take up to 40mm and discs are stock.