Poultry Talk Ontario (pto.ca)

I've done it both ways. If you have the space, nesting boxes inside the coop is the best way I've found. The eggs stay slightly warmer in the winter. Good luck with your design.

Our hens used their external nesting boxes last year. However, not wanting to do a lot of snow shoveling in the outdoor enclosure this winter, DH built an enclosure and hen house in the barn. I'm glad he did, too, because the temperatures really dropped compared to last winter.

Before I post my pictures in a different thread, I do have to say that I like the external nesting boxes. The setup that my husband built has the nesting box that is at waist level and removable, as well as a slide-out and removable tray floor. It's handy when cleaning.
So, unless the hen house nesting boxes are surrounded with lots of space to move around in to clean, etc. I'm happy with my set-up.
I posted pictures of our set-up under In the Hen House > Photos.