Wow, been a long time and I can’t remember it already since we moved from cPanel to DA.
Of course, you need to announce it first and provide options for your clients. Reseller and Shared Hosting is easy for us and most of our clients don’t care since they trust us
For VPS and Dedicated Servers, yes, definitely you give them options. Stick with cPanel and tell them the new prices increase or give them the option to move to DA and save money.
In the end, do what is best for your clients so your last decision will be in your hands.