Both are beautiful. I prefer the cyan; you can pair it easily with jeans, can be worn around the year. Yellow for me is summer bag mainly. In my experience I have found blue bags easier to pair With clothes and shoes than bright colours.
Yellow! It works with jeans, navy, grey, tans and black. I love the cyan, but it is not as versatile as the yellow. And it is not just for summer...it is for any day you need a pick-me-up or a slice of sunshine! Which happens a lot in winter.