KeywordSpy is appropriate for most Internet Market research companies. I would not suggest it for a corporate marketing department unless it's a company with a very larger budget. This is also not a tool for small freelancers even though there is a free option, to get the best benefit of KeywordSpy it's best to use most of its features and options and this can get pricey.
It is great for just tracking keyword performance. The other features are nice but are not the most useful when compared to other for robust tools. The easy-on-the-eyes interface and the fact that keyword data can be updated in less than 3 hours after a bulk upload are why this tool works for lower-maintenance websites.
Most SEO and market research tools offer what KeywordSpy has but are not as detailed and in one place. Consequently, where you can do everything at KeywordSpy, with other tools you find you have to purchase multiple tools or subscriptions from different providers which also don't integrate with each other. KeywordSpy makes your research easier and more efficient.
While both are billed as keyword performance tools. Conductor is a much more robust tool and not totally necessary for lower-maintenance websites. Rank Ranger is perfect for our clients that simply need keyword tracking and reporting on a monthly basis whereas we utilize Conductor for in-depth content recommendations, on-page and competitor analyses.