When you change the name of the URL that you're devices are supposed to trust, they need to re-learn how to trust that server since it will then be unrecognized. In a nutshell, anything you've enrolled will need to be re-enrolled. If you're in a testing phase the impact should hopefully be minimal, but if you're making this change while managing active devices you basically have to treat it like migrating MDMs.
Making this decision early on in your evaluation/testing phase will help prevent pain later. Though that being said, pick something you're happy with that won't need to change.
If you go with a dedicated hosted (jamfcloud) solution with premium support/services you can actually use a custom domain name of your choosing, like something that matches your organization's domain name(s). Depending on the size/scope of your deployment that may or may not be worth the extra investment.
