I have both a carbon and a ali bike.
I very much regard my carbon as a labor of love, always looking to upgrade the bits and peaces on it. My ali bike is very much my workhorse bike.
As to which is better....Nether. In fact Id go as far to say an Ali bike is every bit as comfortable as my carbon, maybe more so due to it actually having a fatter more padded saddle than my carbons super light, not very padded saddle.
Oh...my carbon is lighter though - but this is a much todo with not just the frame, but all the other components Iv shelled out on