Ask HN: Useful tools for picking SEO friendly URL's, and Google discrepancies

I've been doing some research to find some URL's that would be SEO friendly for Google... I figured that I would look for some information on the popularity of search terms and have come across 2 different tools provided by Google:

Google Trends (http://www.google.com/trends) Google Insights for Search (http://www.google.com/insights/search) Adwords Keyword Tool (https://adwords.google.com/select/KeywordToolExternal) Search-based keyword tool (http://www.google.com/sktool/)

For the keywords: forex, forex trading, forex market

I obtained the following results (first two are relative, second two are absolute values)

  Term     forex      forex trading   forex market
  Trends   1.00       0.10            0.02
  Insights 83         8               2
  Adwords  11,100,000 3,350,000       135,000 
  SKTool   n/a        66,000          10,000

Normalizing the data with the lowest result set at 1:

  Term     forex      forex trading   forex market
  Trends   50         5               1
  Insights 42         4               1
  Adwords  82         25              1
  SKTool   n/a        7               1

Trends and Insights have decent agreement, but Adwords and SKtool have a large variance, especially in the absolute values (3.3M searches is a lot different than 66k!) but also in the relative sizes. I'm not sure why SKTool wouldn't generate a result for "forex" and all of the configurations were set to "all countries, all languages" for the past 12 months.

This link (http://www.google.com/support/sktool/bin/answer.py?hl=en&answer=114875) explains the difference between Adwords and SKTool: "You may also notice that some of the data (like such as the monthly search volume) may vary slightly between the two tools, which is due to different methods of calculation at this time." Perhaps Google's definition of "slight" is different than mine.

What are everyone's thoughts/insights on this data, and more generally, how to best go about choosing a URL and building a business around popular terms?

Cheers, Matt