Bookshelf vs diffuser panel. Who wins?

OP,

The cylinders are tube traps. I have owned a pair for 25 years. With my current room (large) they are not so important. But in smaller rectangular rooms they are. In side is designed to face outwards and reflects high frequency and midrange. They trap bass. They can also used in the middle against the front wall… and at other reflection points. 

@fleschler 

Sorry to hear your story. Love to see your systems and venue.

You may have heard me talk about my room. I just really lucked out with incredible acoustics. Large highly asymmetric room. 

I love books / bookshelves and we have nine floor to ceiling bookshelves in our house… after getting ride of half our books. Most newer stuff is accumulating on iPads now. Nothing more comforting than to be surrounded by knowledge. My partner and I dearly love knowledge and share 6 college degrees between us.

Well. They are kind of the same. The real question is how much diffusion is best for your speakers. These are floor to ceiling bookshelves? You can pull books out an inch or so randomly changing the book surfaces to be highly irregular. 
 

Different speakers require different ampunt of diffusion. You can experiment by throwing heavy blankets over the bookshelves. See my systems. A thick wool oriental carpet has really improved my system. Pillows across the bottom killed the fan noise from my amp and low reflections.