2. The second category are keyword tools based on the competition. One of the first things to determine is not only who the business competitors are, but who the SEO competitors are. Keyword research can be done by simply doing research on high-performing competitors. Some of my favorite domain-based keyword tools are SEMrush, SpyFu, and BrightEdge's Data Cube.
This is one of the best articles on Keyword research tool that I have encountered. However, To add more to this, I just wanna point out a tool (LSI Graph) for an outstanding long tail & semantic keyword research. After the recent Google algorithm, Google is now, however focussing more on context & semantics than keyword alone. What do you think about it?
It would be great if you can provide comparative analysis of this tool with Google Keyword Planner. Since you’re using this tool so you can provide best comparison. One differentiation which I understood is that this tool works for yahoo and bing as well whereas Google keyword planner works only for Google but Google being a dominating search engine, gives the highest returns, so only this reason may not be enough to buy it.