These two photos are of the same adult American Oystercatcher (Haematopus palliatus) in sequential order taken at Fort De Soto County Park in Florida. I was laying in the sand while I created the images to get a low angle and the bird was on a ridge elevated slightly higher than my location. I had beautiful light and did not need to use any exposure compensation to have nice details in the darks and the whites.
When photographing with waves in the background a split second can matter because of the fluid movements of the incoming waves. In this frame the closest wave is just about to crest thus it created the darker horizontal band of sea green just below the body of the Oystercatcher.
In this next frame the wave had crested and rushed towards the shoreline creating a smoother blue background without the sea green horizontal band.
Is one background better than the other? Personally I don’t think so, I find them both visually appealing. It is just a matter of personal taste.