I would stick to free tools while deciding on what factors you find important for your campaigns. Once you have a set selection of important variables that you find important, then find a keyword tool that supports this subset. I will list a few of the tools that I use as stand alone tools for specific information.
1. Google Adwords Keyword tool external (legacy edition) - Good for getting monthly search volumes, Adwords CPC values and Trending information.
2. SEOQuake add on for Firefox or Google Chrome- For competition research, this tool does a great job of adding important information to your keyword competition Google searches. I personally feel that the number of back link per page and domain are probably the most important information offered.
3. For initial keyword lit creation, I prefer to use any of the various Google Wonder Wheel scrapers that can be found online.
I hope this helps a little. All in one tools are great, but only if the return information that is useful for your campaigns. I am partial to Market Samurai in the initial SEO and content creation phases, and to track with WEBCEO for continued optimization and rank tracking.