Welcome to our forum.
Do you need to drop your Ph or alk a lot or just a little?One nice thing about MPS is that you can use the spa pretty soon after you use it. If you shock with dichlor, you have to wait a bit to use the spa, until the chlorine reading is low enough.
chiming in my data point: I use MPS as a shock (about every 2 weeks or after about 12 soaks.I use dichlor as my sanitizer, and add it AFTER I soak.