AppFollow is well suited if you only operate in a few app store countries and don't have a high volume of keywords that you are looking to rank for. This is, of course, the free plan. Besides that AppFollow is well suited for communication with other apps - they have an open API and other connections to a ton of third-party analytical tools.
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.
While App Annie is extremely robust and pulls in data from acquisition channels, app stores, and elsewhere, it can be quite overwhelming at times. If you are looking for more simple and just keyword positioning then definitely look at AppFollow. Apart from the two platforms themselves, I've had numerous contact experiences with both AppFollow and App Annie. The winner is definitely AppFollow with a less aggressive approach and a higher willingness to go above and beyond to make sure all questions are answered. With App Annie I was bombarded with a ton of sleazy, sales emails to purchase their product.
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.
