PPC has major effect to get the leads but the disadvantage is whenever you pay you will get the leads but when will stop paying, you won't get any leads. But with SEO your leads going to be increase day by day.
PPC is paid service and one has to pay for it while seo is also paid service if you get it done by hiring experts. PPC is more expensive than that of SEO.
Because that source from PPC is not organic, but paid traffic, that means money. So when you still pay you have traffic, when you not, immediatly reducing traffic will happen.
SEO will help you bring an organic one, which means no cost and quality (cause they come to your site naturally). Besiades, when you use PPC, you have to think about how to convert your paid to organic, so you won't use your money again to attack the same group that you paid to visit your site before; and SEO will help you that