When my daughter had a severe dermatologic reaction to ivy and oak, we went to urgent care. Had she had an anaphalactic reaction, I'd have called 911 and we'd have gone to the ER. It happened on a weekend when the pediatrician wasn't in or I'd have taken her there but she quickly needed a steroid injectection and PO steroids among other things.
All 5 of my kids have fractured something at some point, normally in the course of playing sports. They've all been simple fx's except one of them..... they all went to urgent care except the one and she went to the ER for that one. When my youngest took off the end of her finger in the dead bolt of the front door....we went to the closest ER. They sent us to Children's after getting her taken care of to have it reattached.
I just take the more urgent than emergent issues to urgent care and more serious issues to the ER. My insurance company is happier that way and so is my wallet insofar as copays. Besides, urgent care centers are usually faster than ER's..... Just my