What are the best search engine marketing tools?

Search Engine Marketing: How reliable are tools like Spyfu, KeywordSpy, SEMRush and Ispionage are for estimating CPC? What are pros and cons of each?

• These look good for knowing the keywords, but in terms of estimating CPC, I am getting substantial differences in data obtained from their trial versions

• Answer:

  Each of these tools has pros and cons along different dimensions, and all can be useful in certain cases, but I would not trust any of them for gauging CPC. There are a few reasons: I have never found them to be accurate, not even relatively for different keywords using the same tool--that is, we have profiled terms that we know have wildly different CPCs and fed them into the same tool and received identical estimates, and vice versa. Reporting one CPC is an oversimplification that requires many assumptions, and these are not well described or documented in most of the tools. CPC is variable, and can deliver a gradient of traffic. As I said, these tools can be useful for various things (for example, gap analysis versus your competitors, or shoring up your long tail). But if your only goal is to get CPC estimates for a manageable set of keywords, use the free AdWords estimator, and then finally spend a small budget to get actual results.