This question is almost impossible to answer without running campaigns for both.  With SEO you rank organically and dont have to pay per click to your site but PPC allows you to pick specific demographics, behaviors and keywords that allow your marketing to get very granular.  Typically if your site doesn’t rank, we suggest starting a SEO campaign and also start a pay per click campaign at the same time since SEO is not an overnight process where PPC is.  With both campaigns we install conversion tracking to track the success of both campaigns and over time we can then pick a clear winner after we analyze the data but most companies that are trying to grow will always do both SEO and PPC.