I use google analytics to analyze the visitors , no of pages visited and other stats for my web site Skill-guru I have also added my site on compete.com . I was looking at unique visitors count on compete and there was a big difference between number of unique visitors reported by google compared to compete.
Do they use different parameters to count the unique users ?
Google Analytics is much more accurate than Compete.com because GA uses a tracking pixel and Compete does not.
Compete is just an estimate, and I've seen it be wrong by an order of magnitude. I wouldn't trust it at all if you can help it; if you do look at it, just count the number of digits in the number.