Is there actually a design difference? I haven't read any specific info, but have read some general studies and was under the impression foil just provides a better storage environment - as everytime you pop the lid on a barrel of strips, more air/moisture etc gets in.
I use optium and prefer the foil - makes for a much less bulky kit.
My biggest issue at night is the dark, although the Libre reader being back-lit helps a lot more than juggling a phone and my old optium neo