Like the others said engineering has a lot to do with it along with frame material. That said, I have the experience of having all 4 frame materials within a fairly short amount of time and I currently ride carbon (race bike) and ti (rain bike - and before you razz me for having such a fancy rain bike, I
won this bike last year in a season long points contest
)
My steel bike was touring geometry and it was really too large for me. To tell you the truth I don't remember this bike absorbing a lot of road noise, though the handling was very stable and the braking was also very stable. That I'm pretty sure had more to do with the geometry than the material.
From that bike I went to an aluminum bike with a sportier geometry, rode for a while on a bike that finally fit, found myself to be much quicker and started racing. Since it fit me this bike was worlds away from my old one (not to mention about 5 lbs lighter). I can't say I really noticed this frame being any more harsh than my old steel one, but to this point I did not have any experience with ti or carbon. After only about a year I pretty much decided that while this bike was a big step up from my old steel bike it was still too heavy and being a triple it was not so suited to racing.
My next bike - a Specialized carbon bike. I love this bike. It's my race bike and it quick and lively. It must be a lot stiffer than the alu one since it sprints like a dream (I'd never won a sprint until I was riding this bike). It soaks up a lot of road noise and rides very smoothly. I don't find it to be dead feeling. This one is also a good bit lighter than the last bike, again by about 4 or 5 lbs.
My rain bike - a Ti-cycles Ti. I've been using this one as my rain bike. It came with 650 wheels unlike any of my other bikes so the geometry is different. (I'm a weird body type - though I ride very small bikes -44 with 700 wheels, 47 with 650's - I seem to fit the small frame with larger wheels better. The saddle on my Ti bike is pushed all of the way back to the point where I probably ought to get a setback seatpost since though short I have proportionally longer legs..) This one rides so smoothly the only bumps you feel are big ones and I haven't even put the carbon seatpost I bought for it on yet..With the way I have it built up its a little heavier than my race bike, but not by much. I don't find that it is quite as lively as the carbon bike as far as sprinting or climbing goes, but that could be more that the geometry of the other bike suits me better, since at my size I'm less likely to flex any material.
So that's all pretty subjective, but its my experiences. I have a lot of team mates who race ti and do just fine, climbing and sprinting. (oh - but the indestructible ti frame may be a bit of a myth - one of my team mates actually broke hers earlier this season and I gather that you can't fix it! since she had to replace the bike) I chose my carbon bike more for the fit than anything else - that and high end bikes in my size are very difficult to come by, especially with 700c wheels.
