- RankTracker, gives personalized results
- SerpBook, very unreliable in many cases
- SerpFox, I thought I found gold but in sporadic cases it's VERY wrong, for example a client comes to me asking if I can rank his site, I check his current rankings and back link profile and see he has quite a few links but ranks at #438. So I tell him I think you have some sort of penalty as you should rank higher with such low competitive keyword. He answers me that he's ranking at #12 instead of #438. I start to check manually in Google incognito and indeed he shows up at #14 for me (server location depended of course).
- SEOmoz, accurate I think but extremily time consuming to work with when having many clients / sites to track, and updates the results slowly.
What have you found to be the most reliable one, please one that I not listed here.