my addiction

I have four pairs of birkenstocks.
classic (arizona); clog (boston); one strap (gizeh); three strap (milano)
I lived my life in them - starting with a pair of birkenstocks that my mom wore in university. When they finally deteriorated, I was required to go out and buy my own… this was in about first year university. That's when it started. then i amassed my winter pair (the boston), my dressy pair (the gizeh), my walking/hiking pair (the milano) and my standards... and they are all wonderful.
I have compiled 4 pairs… and I struggle every time I walk into a shoe store to not pick up another. However, I have recently given myself the go ahead to purchase one more pair - the justification? They are nearly the only shoe I wear outside of work.
So. What do I buy? these are my four options.
gizeh in stone; salina; zurich; cancun