Welcome to the forum @Mike Tucson
PSA is good at making most AR-15 variants. I have purchased a bunch from them. Their large frame ARs are not always as reliable. The reason they have AGB is because they use inferior carbine recoil components and have a small gas port. A properly balanced gas system and recoil system should not need an adjustable gas block unless you shoot suppressed.
There are many threads in the PSA section of the forum that go over the issues commonly observed and the fixes that are needed for them. Look there before making a decision. Not all PA10s need help to run, but we can help get in running correctly if you go that way.
As to your question of rifle vs. mid-length gas system, I have used both. As long as the gas to cycle the gun balances the proper recoil system, there has been little difference in my experience. Others may other other views.
I can offer no input on SS barrels.
As an aside, DPMS is now owned by the same company as PSA. New 308ar rifles are likely to be the same as PA10s.