The Display Planner tool replaced the YouTube Keyword Tool in 2014, and can be accessed from the Tools section of your Google Ads account. Although it's a little more involved than entering a keyword into the YouTube Keyword Tool, the Display Planner offers some great functionality for making the most of Display campaigns, including keyword-driven video ad campaigns on YouTube. The Display Planner also offers precious insights into the demographics and interests of your audiences, allowing you to create highly tailored Display campaigns.
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.