Contrast Ratio and Visible Differences in Store

I went back 'again' to apple to play with the phones and on each 'pair' (pair being 6 and 6+ next to it) in each color in the store, the 6 to me clearly has a whiter cleaner white background in Settings, mail, or anywhere there's a light background. The Plus is noticeably grayer/dimmer. I checked each phone's brightness and auto-bright and they were all the same.

I noticed weather on the 6 was a lighter happier blue than the Plus.

I am assuming this is the contrast ratio difference? The 6 has a higher ratio than the Plus. I just didn't think the number difference would be very visible but I think that's what I was seeing. Else perhaps the screens are just different in tone?

I did prefer the perceived brightness of the 6 and the cleaner background colors. Anyone else notice this? It was instantaneously noticeable to me.