What is different between itms vs itms-apps when opening url from device
Using itms-apps: will leads you to App Store directly.

Using itms: will leads you to App Store page in iTunes Store. You'll see "App Store" as navigation title and a button links you to App Store on the upper right corner.

I used to use itms: in my app. But I found that app status on iTunes Store was sometimes not up-to-date as App Store was. I haven't confirmed what caused this but now I use items-apps: instead.