I would trust Google more than Wordtracker, because they are a search engine and Wordtracker not.

Remember to use the "exact" option in Google keyword tool to get the correct number, and that the amount of monthly visitor is only an estimate.

I'd go with Google's free tool. I've seen the same thing happen with a keyword tool used to pay $60/month for. It's called Keyword Discovery. I don't use them any more though.

I still use key word discovery and still get results that are premium. Word tracker has a great data base, but they are not my favorite any more. There are many other key word tools, but you really do get what you pay for in many ways.

Perhaps, you should create your very own adwords account and then you will literally get the actual total number of hits and impressions. OK so this data is a real eye opener. Do out yourself and tell me what you see.

Wordtracker is pulling its data from different sources.

Use the Google estimator more but the bottom line is: never trust search volume estimates. It's OK to use as a scale but not an absolute number.

On GKT (Google Keyword Tool), are you searching with only [exact] keywords turned on?

You should believe on google adword.Because maximum people believe this and getting result from this tool.

Comparing WordTracker with Google, you placed WordTracker at a higher position. That's enough I think. Google is Google there is no comparison.