The difference that first comes to mind between Italians and all the others
is INTENSITY.  The Carniolan and Caucasian colonies I've had never seemed
to match the intensity and vigor of Italians.  Maybe it comes from all
those thousands of years foraging in oregano and thyme :)
 
A more tangible and rational difference is winter brood production and
spring buildup.
 
Italians are from a warm temperate climate with mild winters.  Consequently
they don't always completely stop brood rearing even in cold winter
conditions.  They maintain a large winter cluster and expend stores trying
to maintain a small brood patch in the center of the cluster.  This isn't
ideal in a climate where you have a lot of snow and cold weather.  Even
though it isn't ideal, they seem to manage.  I always kept Italians in
Idaho (sometimes as cold as -20 F) and Seattle (sometimes as cold as 16 F),
and they did fine.
 
On the other hand, Carnies are from the mountains of central Europe where
winters are much more harsh.  They shut down the brood nest in the winter
and maintain a smaller winter cluster to save honey stores.  You would
think this would put them behind the curve in the spring, but they build up
really fast and catch up with the Italians by mid spring.  This rapid
buildup tends to encourage swarming.
 
I live in a climate similar to Italy, and I don't like Carnies for my
location.  We only have a few weeks when the bees can't fly and those weeks
are scattered over about 3 months.  Even when they can't fly, it's more
because of rain than cold.  There are minor nectar flows throughout the
year, and buildup starts in December.  I reported the very first swarm on
the Bee List on February 24th this year. I see bees foraging on Eucalyptus
and other available crops every month of the year.   It drives me nuts to
see a Carnie or Caucasian hive languishing through the balmy winter months
because of an internal clock designed for hard weather.
 
The Utah Rockies are a different story - Much more like the Alps, where
Carnies came from.  I didn't know enough back when I was in the Bitter Root
Mountains of Idaho to try Carniolans, so I kept Italians there.    I don't
have much experience with Carnies in cold weather, but it makes sense that
they would be a more winter hardy choice in such a location.
 
A few other minor differences are that Italians propolize,  rob, and drift
more, Carnies are a little less productive and a little more gentle on
average.
 
My suggestion is that you start with one or two of each and see what you
think.  Pretty soon you'll end up as strongly opinionated as the rest of
us!
Michael
----------
>...Their are two different
> varieties of bees I am looking at for this springs hive.  They are the
> Italians and Carniolans.  I live in the rocky mountain just south of Salt
Lake
> City (Utah the Bee Hive State).  Can some of you talk about the
advantages and
> disadvantages of these two strains.