You can't go wrong with either course. John is a traditional calligrapher and teaches a very formal version. His script is second to none. He is also a lefty and uses an oblique so if you are a lefty, this may be helpful. He takes his time and reviews each letter very carefully. You get personal feedback on your own work from him (this is amazing). He is a very kind man and an excellent teacher. I recommend his first course. The "advanced" one I felt was just more of the same.
Schin is an incredibly talented calligrapher, has a fresh, unique approach and dives into flourishing. Her classes are fast paced and super fun. Her handouts are fantastic. So if you are looking for something a little more contemporary and fluid, and less formal, this may be the one to choose.
If you can, try both! You will learn a great deal from each teacher.