My 853 steel bike was the stiffest, most uncomfortable and downright bizarre handling bike I've ever owned. Whereas my Merckx Corsa Extra (Columbus SLX steel) is one of the most pleasant to ride bikes I've ridden. Comfortable, as stiff as it needs to be, fast and predictable. Seems that Eddy Merckx knows a thing or two about designing / approving a bike!
My Cannondale CAADX is also very comfy, on 28mm tyres, but lacks some of the stiffness of even the Merckx. I think that's probably due to the long chain stays. My Canyon Endurace carbon bike is just wonderful. Light, stiff, comfy, fast, all the cliches. The handling is sublime, on a par with the Merckx but it weighs 2.5kg less! Who would have thought that a company that supplies two world tour teams knows how to design bikes?
So, that's a long way of saying: concentrating on a material is daft. The only given is that steel will be heavier than aluminium which (in the main) will be heavier than carbon fibre. All other aspects, such as comfort, lateral stiffness, etc., will be down to the design of the frame, from the geometry to the tube profiles. And the wheels, and especially the tyres, you run can make a big difference. I rotate tyres between bikes quite often, but even then I don't think I've isolated the effect of the tyres.
The only way to tell is test ride.
