Art Wall: Gallery vs. Shelf

I really can't decide what look I like better- art displayed in a gallery style or layered on a shelf?  I have been waffling between the two styles for a while now.

I"ll see an image like this:

....and I am enamoured.  

Then I'll come across an image like this:

...and my jaw will drop.

Which makes me me wonder,

gallery...

...or shelves...

...gallery...

...or shelves...

...gallery...

...or shelves...

I need to come to a decision as I need to place art above my sofa.  Arg... This decision is just too hard.

 Which look do you like best?  I need to know!

{images via Pinterest & Sarah Richardson Design}