The main difference between Windows 10 Pro and Enterprise is that the following are features are only available with Windows 10 Enterprise:
Start Screen Control with Group Policy
Windows To Go Creator
While you can join Windows 10 Pro edition to an Active Directory domain, it seems wise to buy Windows 10 Enterprise to avoid prohibitive costs in future if you think you might want to use any of the above Windows 10 features.
For a full comparison list of differences between Windows 10 Pro Vs. Windows 10 Enterprise, see this Microsoft article.