I would not consider that an apples-to-apples comparison, because Ionic is primarily a component library, whereas Angular is a framework.
So you could ask if there are compelling reasons to use Angular instead of React, or Ionic instead of Angular Material.
I’ll leave the Anguar v. React debate alone, so stop reading unless you’ve decided to commit to Angular.
When it comes to Ionic v. Angular Material, I would say that unless you want to deploy on touchscreens, I would go with Angular Material. I have developed many app suites that consist of variations on the following theme: one admin app intended to be used on a desktop browser environment, with a pointing device, physical keyboard, and plenty of screen real estate, and one field app intended to be used on a mobile device. They share a common backend. Sometimes one wants to run the field app in a browser, and sometimes one needs to run the admin app on mobile, but the UI design tradeoffs are definitely not intended to cater to those situations.
I’ve had better results using Angular Material for the admin apps and Ionic for the field ones.