May depend on little on how much you are going to use it and state of the roads etc where you ride.
I have ridden carbon road bikes for about the last 4 years and have had 3 of them they all ride differently but all of them including even my stiffest and superlight Tour level frame (Felt F1) provide a much more comfortable and compliant ride than my previous top end triple butted aluminium job.
The difference when you first ride a carbon frame is substantial – really like riding on a magic carpet.
That said if you riding is limited to perhaps 2-3 hours rides then alu may not cause you too much fatigue. Although personally I would say the benefits of carbon are there from the off and not just on longer endurance rides.
No looking back for me once I switched to carbon. I also prefer carbon over Ti from a ride perspective although accept Ti provides the classic timeless look etc