If you said “paid”, you’d be right, at least according to this study outlined at Clickz.
Perhaps not overly scientific, but it illustrates a couple of points worth considering. With paid ads, you can control the descriptions, which as any good marketer knows, helps with conversions. Secondly, since people know the PPC listings are advertisments, they are probably likely to be clicked following commercially-oriented queries.
The organic links tend to be high credibility, especially when looking for information, but the surfer who is looking to buy risks wasting their time if the snippet doesn’t relate to a purchase process.
But then, why choose? Having the best of both worlds, if you’ve got the time and the talent, is probably optimal.
And can the majority of surfers tell the difference anyway?