ok thanks to all of your opinion about this

I use Alexa, as it shows you the traffic history of a site and lets you recognize trends easily. That alone is the best reason to have it installed.

Personally. I like and use both often. Compete for overall traffic of competitors. Alexa for traffic ranking, age of domain, and link profile.

then they are not crap at all

Hi just signed up. I would like to share my knowledge with you all.

Both Alexa and Compete have thin data and are not really accurate. You can use them to get rough indications on traffic and keywords, but don't take them literally. In many cases, I've found them to be way off the mark.

If you are looking for which is "better", I'd say compete.com since they at least try to clean their data and normalize to some sense of reality. Even then, their data is so thin that I'm very careful about using it. Alexa is mainly a sample based on their toolbar, and is skewed to the audience that uses it.

If you really want something better, use other tools that have more complete data. For keyword research, the deepest data right now is from Google's keyword tool.

I think Alexa is best because we can check our website performance day by day!