Macro with flash or without?

I've been shooting macro shots for years using only natural light, but in the last year, I've been experimenting more with flash. Still though, I find myself wondering to what extent flash makes a difference. Here are two shots taken with the Oly 60mm 2.8 macro, one taken without flash, and one taken with. Both converted in ACR. Can you see a huge difference? Can you tell which is which?