ive got both - i prefer black in the new minis with the blackish reverse too
this - need more shoes in rotation + shoe trees to help with the between wear
1) if you put on new pair on just the front rather than heel it changes the balance of the shoe and put pressure on the arch and heel attachment. If you do both it makes the sole feel alot thicker (imo). Ive done both - the first one my shoe at the heel cracked, the second made me look like i had really thick soles and were ugly so i never wore them
2) if you put on an old sole i find that water still impacts especially around the ball of foot and where it bends (because 3mm above the topy is the worn leather from before) and it gets in and weakens the mid flex point of my soles.