I have used a 20 gauge Montefeltro for the last two bird seasons.
Like it so much that I sold my 20 ga Yildiz O/U to maximize my Montefeltro time.
I hit more birds with the Montefeltro than I did with the O/U, mainly from having the 3rd shot.
(Used what I made off the O/U to buy a Benelli Supernova because I wanted some heavy artillary to compelement the Montefeltro.)
I like that it can be set up for a lefty; reversible safety, shims for adjustable comb and cast.
I chose it for the interia drive, but never had a gas gun so I can't say that is better; appears to be easier to clean.
Pretty wood.