Of the two blues hands down Ultra Blue looks better in my opinion. It has a little bit of flop to it and the hue of blue/aqua changes depending on lighting conditions. In bright daylight shining against the flake the color pops a bright aqua-like color and on low light or overcast the hue is a bit like a bright royal color. Brittany Blue is not as dynamic in terms of color changes in my opinion.

Here are some examples in different lighting conditions…