Which event to choose?

I’m curious as to what the Jellies would choose in this situation. A summer weekend and you have two events planned. An evening picnic with friends on Saturday, and dinner at a casual restaurant with a different group of friends on Sunday. Both events have been planned for a few weeks. On Saturday the weather looks a tad threatening, so the picnic organizer changes the date to Sunday. All other things being equal, do you: A) Go to the rescheduled picnic and cancel on the restaurant friends?
Or B) Tell the picnic people you can’t make it because you already made plans with the restaurant group?