I'd definitely still go. It will take away some of the magic of the performances in front of the castle stage, but it will still be a great event, and maybe it won't be as crowded.
I will never forget seeing Chris Tomlin in front of the Cinderella's Castle in 2012. He is one of my favorite artists and seeing him in my happy place will be a lifelong memory.
Part of the reason this memory was so special is because it was in the Magic Kingdom. Anywhere else would be like seeing him...anywhere else. And it would be less expensive anywhere else. That makes my decision for me.