Bookshelf vs diffuser panel. Who wins?

@jumia 

where is the book case located?  

side wall issues can be greatly minimized with speaker positioning.  

@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. 

Guys: as with everything in life, there is no free lunch. Bookshelves, rags, towels, blankets… you name it. Been there done that. There is no substitute to real room treatments. Let’s not fool ourselves. Yes, we all want to save money AND effort/ work.

Good diffusers will be much more effective than bookshelves by producing a 3-dimensional airy sound in the midrange and treble. That’s the main difference when introducing diffusion in the room.

Sound-wise diffusers will win. Practicality and aesthetically bookshelves have the advantage. Although they might not bring a large impact as proper diffusers, they still bring some and it's better than none. On the scale of 10, if diffusers score 9, bookshelves score 4 or 3. Better than none.

How about a few big towel racks on the wall. 
 

mr fleschler, awesome info about your book collection.  My mother had lots of books and she gave them away to the library.  To my horror she gave away lots of signed books.  I'm sure many were first edition really nice.

It seems in the 30s and 40s lots of authors signed many of their books I guess.  I have four books signed by Carl Sandburg.  He liked Lincoln a lot. 
 

Horrifying experience to treat your room. Maybe it's OK now