Hi Nichole! I've been a long time SFDC user and strongly recommend that you use SFDC campaigns to track prospects who have qualified for Marketing activities such as tradeshows, webinars, online advertising, web, etc. The benefit is that you can track campaign ROI and determine what Marketing campaigns are influencing the most closed/won deals.
SFDC Activites are used more by the Sales team to be able to track sales follow up such as calling or emailing prospects.
Hope this helps!