Italians are, as Marion Ellis called them one day, "brood rearing fools". Carniolans are more frugal. If the weather is decent the Italians are rearing brood. The Italians overwinter with a bigger cluster than the Carniolans and eat more stores in dearths because they don't have sense to cut back. The Carnis fly in colder weather, stop rearing brood in a dearth and cut back to a small cluster in the winter and need a lot less stores.
I like them both, but I prefer the Carniolans for my climate. I'd say in the deep south the Italians would probably do better.