So I don't have fresco, nor have I ever tried it so I'm not sure of all it can do. But speaking from my experience, I have an old version of photoshop and can do pretty much all that's presented in the course with it. So perhaps if you're planning to work a lot on a mobile device it can be worth getting fresco (although there can possibly be less expensive apps that can do just fine for that too), but otherwise I don't think you should have any issue with only photoshop.
