Purely in terms of weight, you're not going to notice much difference. Weight matters most when you're climbing, but you are talking about a difference of less than 2% in the total weight you'd be hauling up the hills. That isn't totally insignificant, but it isn't huge, either. On the flat it will barely matter.
There'll be more noticeable differences in the ride. Homeyba has mentioned that CF tends to dampen road buzz better than steel (or aluminium), but much also depends on the geometry of the individual frame, the choice of tyres and so on. Some steel bikes will be less fatiguing over long distances than some carbon bikes. For doing long distance stuff (bear in mind I don't ride the sort of huge distances that Homeyba covers) I'd be inclined to choose the bike I felt more comfortable on, rather than insisting on a specific material or worrying about a pound here or there. Other things being equal, obviously I'd go with the lighter option.