The difference is big, see below:
Deactivate a User
This is a much safer option. When you ‘Deactivate’ a user’s profile, you are basically just de-activating their Username/Password so they can no longer log in and access their training account. This does not delete the reporting information we have on them or remove them from your account or our system.
To Deactivate a user, click "Deactivate" from within the user's profile.
You will probably notice that most of our Reports default to reporting only the results of Active Users but most reports have the option to include those inactive users too. Plus, you can re-activate the person whenever you like! This is great for those organizations trying to control the number of users logging in to their accounts each billing period.
Delete a User from your Account
When you delete a user from your account, all of the information collected about that user over the time while they have been in your account, will also be deleted, forever. This includes all of their course results stored in Reports. Even if you were to re-create that user again with the exact same details, our system will create them with a new user ID which will in no way be connected to the old user account.
Think very carefully before you delete anyone!
To Delete a user, click the "Edit [User's name]" link from within the user's profile. Then select "Delete this person" from the left.