I'd definitely go with USMTGUI to backup the Azure profile, and restore it to the Domain user. Or perhaps even User Profile Central.
Both tools utilize USMT (from Microsoft) and USMT has been heavily optimized by EhlerTech.
We used USMTGUI a while back to migrate our AD users user profiles to AAD and I know for a fact that USMTGUI will also backup AAD profiles.
As you say, the profiles are, basically, the same.
With User Profile Central you can also handle profile migrations over LAN and collect existing users profiles prior to handing out their new PCs.
- We often get the comment that "its nearly as if its my old PC, just better" and we save so much tech and user time setting up stuff.