I think a mix of local SEO and local PPC is a very powerful strategy. PPC can get you results (calls for estimates) within days. You can increase that number and scale very quickly, too. SEO however, is more of a marathon. It takes more time to build up, but if you decide to lower your budget for any reason (for PPC), SEO can help you continue to get leads.
The problem with depending on either one, but especially SEO, is that if Google/Bing changes their algorithm…you might lose everything overnight. PPC is far more predictable, measurable, and less risky. It’s just more likely to cost more.
Like I said, I think a strategy that uses both is best… diversify your source of leads… as long as you’re not paying for a lead service (ie, the leads you get belong to you, not you and 5 competitors!).