Any successful keyword research process involves these steps:

1. Ability to “dig deep” into any keyword phrase and uncover the long tail.

2. Search volume estimates so you know how many people per month are searching for each keyword.

3. Lateral / Thesaurus search options which allow you to go “broad” with your keyword research.

4. Competitive Research that allows you to see the competitive landscape for each keyword.

There are only a handful of tools that meet these requirements: 

KeyCompete manages to do #1, 2,3,4 very well.  Especially #4, since it allows you to download the exact keywords your competition is using in their paid advertising.

SpyFu also accomplishes #1 & #4 very well, since it displays your competitor’s keywords, as well as average budget, and other competitive features.  Although, I still prefer KeyCompete because SpyFu’s competition estimates are sometimes way off.