tough decision! i have seen both, and at some point owned both. i guess it would depend on what colors you typically wear in your wardrobe and whether any of those colors match too much or clashes. i personally am in love with the blueberry but i wouldn't mind getting my hands on the petrol baby spy.
fyi: i emailed the seller about the petrol spy on ebay a few days ago, requesting additional photos. they revealed major scratches on the bottom. i attached the photos that the seller sent me (i hope it's ok to do so!). so please take caution if you decide to bid on this bag. the seller did not disclose these scratches in her auction (in fact, i think the seller claims that the bag is super mint like new, which in fact, it's more like excellent well used with blushing throughout).
sorry if i am of no help in the color decision, but i hope the photos will help with something
