Besides the color, there are other less obvious differences between Italians and Carniolans.

I've worked extensively with both breeds and even spent a couple days watching Sue Cobey artificially inseminate breeder queens.  I even accompanied her on a drone trapping expedition!  We collected traps with hundreds of big fat drones.  Collecting the semen was another story.  I am very glad I wasn't born a drone!   Squeeze, pop, and it's all over!

In my opinion, even though both breeds will produce honey, the real difference between these breeds is in how they handle a dearth or the big dearth, winter.  Carniolans will stop rearing brood much more quickly than Italians.  The saying is soming to the effect that "The Italians made more honey than the Carniolans, but they also ate a lot more".

When I kept bees in the tropics I used only Italians.  Now that I keep bees in Minnesota, I use only Carniolans.  

You really need to determine how you want to keep bees and then use the appropriate breed.

Mark in Minnesota