I believe VPI is generally considered the best, at least in terms of not browning out as much.

As these pictures show, and from what I've seen when I've seen a couple adult axanthics in person, they don't stay as silvery as when they are hatchlings, but they are still obviously not normal bps. I love them!

To me, what makes the prettiest axanthic is when they have a really bright white line between the grey & the black. None of the pics on this thread so far have a great example of that.