I know of a certain niche that has dozens of SUPER seo'd pages with 4000+ links to each of them.. and on SEOBOOK it says its only getting less than 100 searches a day. Also, I've come across a two word term that gets 4000 searches a day and has 277 competing sites. Can these things sometimes be VERY off?
from my experience seobook is pretty accurate but from what i saw it doesnt gets updated often, some keywords that were really popular at the time can decrease - think about it.
I use micro niche finder and the info it fetches me is updated IMO. Unfortunately, I haven't got any experience with other tools.
SEO Book uses Wordtracker which isn't good for many reasons....Find another post where I have commented for exact reasons. Use Google...Again there are numerous reasons, but please find another post because I can't really be bothered to keep answering the same question again and again.
See the sponsored links in a website,if you are seeing sponsored links more than 5 pages,then it is a high competition keyword. If you are seeing upto 3 pages,it is medium and if it is upto one or no pages then it is low competition keyword.