My understanding of the discussion between supported and unsupported barrels is based upon pressure.
No barrel is completely supprorted or unsupported, the unsupported are more unsupported than the supported. [a disclaimer]
An unsupporeted barrel will:
Be more feed reliable in semi-autos out of the box.
Is not designed for a number of high pressure calibers or not reccommended for round that are loaded hot rod. My understanding is that even traditional, lets use the .45 as an example [a very low pressure round], can have case failure if loaded too hot in an unsupported barrel.
Not all brass is equal.
Supported barrels:
Will need some care and attention to insure proper feeding.
Some would even say that supported barrels should not be used in weapons which require reliable feed for self protection [Dane Burns] and others disagree. Certainly supported barrels have been proven to be reliable. The question then falls on the degree of reliability some would have need of.
High pressure rounds such as the 9x23 are best suited for supported barrels IF the proper brass is not used.
Using the 9X23, again, Winchester produces a brass that is designed for this high pressure round. It is a brass that can be used with unsupported barrels.
Even though this is true, I would think that the boys that hot rod this small rifle round should use a supported barrel for their purpose.
This conversation is carried over too the likes of the .38 super, 10MM, Super .45 and any round that will be hot rodded to the max or near max.
My 9X23 is not in a supported barrel from STI but then again my needs are not for hot rodding and IS for reliablility. Some of my loads are even softer than factory.
This same thought process is/will be for the .38 super I expect to purchase.
Blessings