We prefer and suggest Long Tail Pro to all our clients. Long Tail Pro is the best long tail keyword research software online. I use their software for researching keywords for everything from social media marketing bios, to page and blog post titles, to headings (H2, H3, etc.), to meta descriptions, to YouTube descriptions, to content/articles, and so much more!
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.