unless the user with no migrated data on it, is the user that was created when you installed OSX, it can be deleted safely. Yet, I assume the migration process created its own user (the second one), so the first user would indeed be the one without data on it.
This is important because the user which was created during installation has administrative privileges. If the second user has been created as standard user (which is the default way), deleting the admin user would damage your OSX installation.
If you open System Preferences and select Users & Groups, highlight your second user on the left hand side of the window and see whether a check mark is activated on the second option counted from the bottom up.
If it is, your second user does have administrative privileges as well.
As a safety precaution it would be wise not to use an account with administrative privileges for all day work. So keeping the first user with admin privileges and the second without would be the safe way to go. Be aware that in this constellation you must not forget the password of the first user.
Hope this helps,