Visit Profiles automatically enters on the profile page. This way, you can extract more information and also perform all the actions avaliable (that being: endorse skills, send an invite to connect and send a direct message).
Scan Profiles gets all the information that is visible in the search results, so it basically gets full name, company name and job title.
We suggest using Visit Profiles as you'll get more information. Additionally, the lead will see that you visited the profile (and there's a high probably that they'll visit you back).