SEO definitely focuses on organic( free ) marketing wherein the results take time to come but are 100% long-run basis.
One-time good SEO will guarantee results in 6 months but will always give quality.
It is something that can be improved on a daily basis like a good habit.
On other hand PPC involves money. The more money you put the better your chances of getting better results. But many times there are chances that you will not get quality leads even after adding a good amount of money.
So I personally feel a mix of both SEO and PPC is really good for companies as it can generate leads with organic and paid both kinds of marketing. But it also matters how good the service or the product offered is.