My positions reported by SerpBook, Serpfox, and SheerSEO are a few hundreds lower than those from Link-Assistant Rank Tracker and CuteRank. Rank Tracker and CuteRank numbers are inline with Chrome Incognito search results (signed out and using US proxies). The fact that there seems a clear division between web apps and desktop programs makes me wonder which group I should trust. While the majority of reviews for SerpBook (and Serpfox) are positive, there are people complaining about them being inaccurate. How does your experience go? To what extent do you trust those web SERP apps? Do their numbers closely correlate with the actual visits?