KW Finder is similar to the Google Adwords tool; it even pulls up similar results, which aren’t as entirely on-point as the immediate results from SEMrush and Moz. From my experience with KW Finder, the searches are a lot better if you put some time into manually adding in filters like negative keywords and additional keywords you do want to include.
As you can see, LongTailPro is pulling data from Google Adwords. WHAT?! So LTP uses a mix of their own massive data (launched in 2011) and data pulled via API from Majestic.com, Moz.com, and Google Adwords (http://adwords.google.com). Once you input your seed keywords, LongTailPro outputs suggested keywords related to your seed keywords, search volume, Adwords suggested bid, Adwords competition, total words, rank value, average keyword competition, language searched, and location searched.
In a nutshell, Long Tail Pro helps you quickly find keywords in bulk based on a seed keyword that you input. In addition to returning hundreds of related keywords, the tool also shows search volume (monthly search volume), advertiser bid, number of words, rank value, and my favorite Keyword Competitiveness (helps you judge the competition and keyword difficulty).