SEO:
- Is free
- Requires hard works when you do it yourself.
- Brings you a lot of targeted traffic if you do it right.
- Still keeps bringing you traffic day in, day out when you stop doing SEO, say 1 month or so.
PPC:
- Costs thousands of bucks if you do not know how to increase the quality score (for ones using Google, who does not?).
- Provides you with instant and highly targeted traffic.
- Stops bringing you traffic once you stop paying your money.