[jimminy]

Try holding a piece of paper over them, so you can only review each independently.

In isolation, for me, the white on blue, has contrast bleed which makes the text fuzzy.

Again, in isolation, the black on blue is much sharper.

Together however, when presented side-by-side, the black on blue feels to be lower contrast. It's almost like my brain is using the black on blue to help compensate the weakness of the white on blue.