Koala! No doubts about it. It holds a lot, cc, driver license, change and $$ bills, while being slightly smaller and fitting perfectly in a smaller bag (pochette, twist pm, etc)! Zippys are too long to fit in any small bag.
Another vote for the ZCW! I would not enjoy the Koala as much b/c I'd worry about the buckle scratching something in my bag or just wearing/ tarnishing/ getting scratched over time.