Blue. Especially with the yellow backing.

Blue for sashing, yellow for backing. Won't it feel great to finish it?

I vote the blue, really brings it together

I vote for the blue also. I think it brings out the intricate design of the blocks and is calming. The yellow is pretty also, I'm just a fan of blue with yellow, not yellow with blue. :)

I prefer the yellow as the blocks tend to run into the blue one and there is no distinct line of where the sashing starts.It also looks fresher and less heavy.

#3 - yellow!

They look great both ways, but I'm leaning to the blue. But the yellow looks so fresh! I guess it depends on the recipient and their colors, as well as the colors of the room in which it would be used.
Have you thought about a 1/8" border or flange in a darker blue around each block to really frame them? Perhaps lighten the blue color just a little, it is kinda dull in color.
My DH just weighed in, he likes the yellow, said it frames the blocks, and that particular blue looks dull. But it could just be the pic

I vote for blue...

Blue...it pops the yellow. Beautiful quilt by the way.

I vote for the blue with yellow cornerstones. The yellow in the picture seems closer to gold, and the darker blue makes the blocks pop. Pretty quilt, BTW.
Sue