@Jeremy-Ross
Oh, great idea about making a mockup cover! I also think it is smart to do it in both styles, however I did that once for another image (between watercolor and digital, see below) and I couldn't decide in the end. How did you decide on your style?
Here is an example of where I tried two styles for the same image:
This is the watercolor version

This is the digital version

I feel like each one has pros and cons and I just can't make up my mind about it. I got mixed responses as well when I showed these to other people with it being pretty much 50/50 over who liked the digital and who liked the watercolor. Is there a process you go through to decide what style will work best for you?