I'm in a similar situation and based on talking with people in the area, both are great districts, and a heck of a lot better than anything in DE or MD. I think Unionville is considered the "better" of the two, though. I did hear recently from a friend that KHS is doing better than UHS in terms of AP testing. I think if you are in either one, you will be fine. Avon Grove is a close runner up in the Southern Chester County competition.