Hi, thank you for entering! Of all of your designs, I like Entry #4 the best. However, including "OPA" in the box makes it a little busy, and it's hard to make out that it's a trillium. Entry #3 is quite nice too, but perhaps change the font so the A in OPA looks more like an A.
I'm not really convinced, though, that purple is the best choice for color.
Hint: Stay away from blue (that's the colour of the Ontario Medical Association).