Typically 3-6 months are needed for SEO work to materialize
benefits
Near-instant - as long as it takes to setup your PPC campaign and
acquire clicks
Relative Costs
In the short term, SEO work typically requires more cash than PPC.
In the long run (beyond 6 months), SEO is typically less expensive.
In the short term, PPC is usually less expensive than SEO. However,
the cost of SEO begins to fall while the cost of PPC remains
steady. After a few months of advertising, PPC is typically more
expensive.
Ongoing Effort Required?
Definitely - in order to be successful long-term, an SEO strategy
must embrace ongoing effort.
Typically, but not as much as SEO. Unless new advertising concepts
are constantly being introduced, PPC requires less effort over
time.
Potential Click Volume (% of searches)
If you obtain #1 ranking on a particular keyword, 30-50% of the
people searching will click on your listing.
Generally, about 2% of the people searching will click on a paid
advertisement.
Scalability
Possible, but expensive. SEO works best when it's one piece of
content at a time, one link at a time. In order to achieve any real
scale, you need a large team.
Easy - Provided you have the ad budget, you can have advertisements
running on hundreds of thousands of keywords in short order.