Eguller I swap between the Avalon 5 and Mystic 4 in my PXG driver. I prefer the Avalon, but the Mystic is very close and often gets in the bag. Just a bit more spin and launch with the Mystic. Honestly, I don't think you'd find a significant difference between the Avalon5 and Mystic5. Pick the color that you like.
I still have 2 extra Avalon 5s from my last Xcaliber purchase saved from future use.
I was tempted to get some Rapid Tapers to save, but I didn't love the first rapid tapers and I already have two sets of iron shafts on standby.