If you’ve collected a list of past clients, nothing could be more valuable. Sending these clients an email isn’t a cold call. These prospects know your product and any promotion from you is an “add-on” sale. Email marketing to your collected list is also very cost effective. Past clients can be your best sales force. If you promote your product using email, your base list isn’t likely to be the only recipients of the email.

Pay per click is beneficial in a different way. Properly targeted, PPC ads reach far beyond your current base to recruit new prospects in markets you may not have considered. Getting browsers to click is difficult as you’ll be competing not just based on ad-copy and design, but on ad placement and density of ads per page, which is out of your control, but these clicks are very valuable. Prospects garnered through PPC are genuinely looking for your product and your chance of closing a sale are very high. If you can use PPC to expand your email list, PPC can be doubly beneficial.

I don’t see one as being better than the other, but instead see them as working in tandem. You’ll always be looking to broadening the reach, while continuing your relationships with current clients.