Go with the pizza shooter. I have been using my 390 for 5 years and have never had a failure. They are the best auto going for the money if want my opinion.
Concerning the Wal Mart AL390, it is different from other field grade 390's in the ways mentioned above plus the fact that it is not equiped with a magazine cut off. This point is moot on the clays range as I do not see where you would ever have to bypass what is loaded in the mag and put a different load into the ejection port. Personally I would miss it at all.
Hope this helps.