I would say a <strong>combination of both</strong> because the more times you can be on the front page, the better chance you have of gaining the client.  It doesn’t matter how many clicks you get until your content is optimized to convert.  So unless you are a “cannot be wrong” wizard of all things electronic and human....  It only makes sense to SEO first, get some clicks and make sure you can convert your clicks before you start paying a bounty on them.  Since you are going to want to SEO at some point  anyways, it only makes sense to build 5-10 landing pages and start rotating them with detailed notes on each result.  The new Google analytics makes it easy to see what content is working and what is being ignored.  Combine the good content of two pages, and see what makes the cut.  Tournament style brackets until you are left with only two.  One with more information and more graphics that clearly shows how much was as a company care about you and one very streamlined : Here is what it does, here is why it does it better, here is why you can trust us, here is what it costs now do it.   By paying some money to the otherwise useless network ads, you can collect some data on male vs female keyword routes and use streamlined landing page where the guys come in, and the more informational complete and we care about your feelings one where the females come in.  You can see 5% even 10% increase with this tactic.  Then start narrowing down to age groups and buying habits.   1-3% conversion is average.  Only because 95% of the people who are running SEO / SEM campaigns have no idea what they are doing.  That is why the top 5% of websites make the lions share of the money online. When you find a SEO / SEM / Design company that has an amazing website, top of all the searches and blows you away......  DONT HIRE THEM.  If they have that much time to work on their own stuff it is because they are only getting their clients 1-3% conversions, and you wouldn't hire a doctor who has a 1-3% success rate.   One more tip, when you find the right SEO guy, he doesn't give you office numbers for the referrals...  He will be sending you to their cell on Sunday, because his clients are happy to answer.

I would like to say that both search engine optimization and PPC advertising are two highly effective solutions to attract targeted users from popular search engines. I would recommend online entrepreneurs to use both these techniques in their marketing strategies. It is better to launch a PPC advertising campaign for recently launched online resources. When you obtain targeted users and convert traffic  into website revenue you will manage to invest more money in search engine optimization and when you achieve SEO improvement for highly effective phrases you will be able to decrease your expenses on search engine optimization significantly. It is better to use both SEO and PPC advertising!

 From a trust perspective, it appears that people trust organic search results over paid ones. I agree with much of what has been said on this thread, both can be used effectively and simultaneously, one for short-term traffic, the other as part of a long-term strategy.

Varies so much on your business... there is a LOT of good advice here... I agree if you have a broad range of products and looking for long term options, SEO... if it's short term action and niche markets... probably PPC will have better short term effects... There is no magic bullet...