Diffuser Panels/Room Treatment Question

How much SQ improvement would a large area of front wall chock-full of wall mounted knick-knacks and small collectibles in shallow (3-4”) shelves provide compared to a similar front wall area outfitted with dedicated sound diffuser panels?  Would it be a worthwhile endeavor strictly from a room treatment perspective?  I got tons of antique tools, coffee cans full of bolts, cologne bottles from the Age of Aquarius to Disco, and a bunch of other stuff that could go up on such a wall space.

Thanks in advance…