I have both a "comfortable" Carbon Fibre and a "hard core" Titanium.
The carbon fibre is a Bianchi "C2C" - designed to be slightly below hard core - i.e. slightly more relaxed posture, has Kevlar in the forks (+ weight but mops up bumps) etc etc. I've done loads of long and big rides on this, including Raid Pyrenean etc. Very comfortable, feels like you can ride it for days on end without undue discomfort.
This year I treated myself to a full spec Enigma Excel Titanium (plus dura ace etc etc), really initially for those dry summer days where you want to go out for a blast. I didn't really think I'd end up using it for "touring" etc. However, I loved it so much that I used it all summer and then took it to the Pyrenees to do my cent col challenge - 10 days of 200km and 4,500m climb per day, it was a real joy to ride over all surfaces, so glad I took it.
So +1 vote for comfy carbon but +3 votes for titanium.
Oddly enough on an audax sometime last summer 6 of us flew off the front of the ride, we looked around and 5 out of the 6 had titanium...