I prefer SEO - because I want my sites to last longer and make money longer. PPC is good for quickly getting to page 1, but will cost ya $$$.
I went with SEO, I'm in a competitive market and to purchase links on my targetted keywords would cost me around $9.00 per visitor more than likely. It simply doesn't seem worth it. I would imagine PPC is great for less competitive markets.
I do PPC 90% of the traffic I'm getting is generated by PPC. But SEO that's hard to get but when you get it you can earn millions of $. PPC is good to pay the monthly bills. SEO is good to pay for a house/Flash car & many other things.
My natural inclination would be to throw money at it, but i've discovered that that doesn't usually work. Hence, I think SEO is a better long-term solution.