The Italians will raise more brood over a longer period of time. They will need more winter stores. They will winter on a larger cluster.
The Carni's will raise a lot of brood in a short time, but they do it more sporadically. They will raise brood in the spring from a very small cluster and build up quickly. They will drop off quickly when the flow stops and they will drop back in the winter to a very small cluster.
I don't think (and I'm sure some will disagree with me) that Carni's are more prone to swarm, but they can build up population more suddenly and surprise you with how fast they run out of room. And, of course, then they swarm.
For my climate I would prefer the Carni's. For the south, maybe the Italians would do better.