I'm waiting to see what Feline says about her quilt too.....
I have tried all the above techniques and QAYG. The first thing I tried was quilting the 2 separate tops using thin battings, then quilting those together. That works, but makes for a thicker, heavier (and warmer) quilt.
Easiest for me was lining up front and back accurately then using a big (not tiny, intricate) overall quilt design.
Next easiest- QAYG.
Kalama Quilts does lots of double sided quilts too....I wonder what her fave technique is.