I have the blocks to diamonds book and have been trying to decide which one to make. I have a couple of UFO's I am making myself finish before I start anything new. Like the quilt I gave my DD and SIL for Christmas. They got a bag of fabric and a promise that it would be finished before they need it in the fall. All I need to do on that one is iron the backing and get some batting. I and going to take it to the longarmer. I have a mystery quilt that has been needing a border for 3 years, and a wall hanging that needs a sleeve. Then I can start something new.
I vote for starting both projects. I think the applique would get a little bit tedious and you might need a break. I love them both and look forward to seeing them.