This is another free tool for keyword research. The tool allows you to combine your keywords in a very easy manner. It has three main match types which include broad match, phrase match and the exact match. You can choose on any of them depending on your keyword search objectives. In addition, you can either use broad modifier or optional keyword or both. Most users are finding it to be a very useful tool in their search for the most appropriate keywords.
1) SEMrush - I believe that among all the 3rd party software, SEMrush has the largest keyword database. Their search volume data is pretty accurate and aligns with the Google keyword planner. Also, based on the type of content that needs to be produced (i.e. informational, transactional, etc.), one can utilize different filtering options available in 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.