Hey Alex – this is a good question. No tool is going to be spot on. My advice is to not look too much into the accuracy of the metrics, but look at it more as a relative measure. I’m finding Ahrefs to be a good barometer for keyword competitiveness, but I’ve also heard great things about KW Finder lately. I think it’ll more come to personal preference. Both are solid options.
Jaaxy uses a combination of search engine data from the major search engines (Google, Bing and Yahoo) and Long Tail Pro get its search data from Google alone (via the Google Keyword Planner tool). While this seems to be an advantage for Jaaxy, you might only be interested in getting information from the number one search engine in the World: Google.
Analyze Keyword Difficulty – Targeting difficult keywords with the highest competition is not always the best idea. The SEMrush Keyword Difficulty tool helps you determine keywords’ difficulties. By indicating a particular keyword’s percentage of difficulty, this tool helps you estimate how easy it would be to seize your competitors’ organic positions in the SERPs.
Because great content requires a deep understanding of the main idea (e.g., “ac repair houston”) and the supporting subtopics that require coverage (e.g., “central ac vs portable ac systems”) and the common issues that users seek answers for (e.g., “freon,” “refrigeration loops,” “coolant refills,” “troubleshooting”), the effectiveness of a keyword reporting tool is only as strong as the SEO pro using it.

Note: the old software version of Long Tail Pro would have spit out several hundred adwords suggestions (many being irrelevant to the seed keyword) for this one seed keyword and then you would have to filter to see only what you wanted to see. With the new cloud version of Long Tail Pro, you set it to show only a certain number of keywords and it displays the most relevant keywords so you have less noise and confusion to filter through.
Most keyowrd databases consist of a small sample of the overall search universe. This means keyword databases tend to skew more toward commercial terms and the core/head industry terms, with slighlty less coverage of the midtail terms. Many rarely searched for longtail terms are not covered due to database size limitations & lack of commercial data around those terms. Plus if those terms were covered, there would be large sampling errors. Google generates over 2 trillion searches per year and claims 15% of their searches are unique. This means they generate searches for over 300 billion unique keywords each year. The good news about limited tail coverage is it means most any keyword we return data on is a keyword with some commercial value to it. And with Google's Rankbrain algorithm, if you rank well on core industry terms then your pages will often tend to rank well for other related tail keywords.
In addition, you can dig into the paid side of search and find out what keywords your competitors are bidding on, and then leverage those keywords for your own organic benefit if you're not already doing so. Search Metrics does this as well, but I've found SEMRush to provide a greater range of keywords and they save more historical keyword data than Search Metrics.
As for the history of the company, as I explained, I created Long Tail Pro back in 2011.  At the time, I was creating tons of niche sites and was doing alot of keyword research and content creation.  I was trying to figure out what types of keywords would rank quickly in the search engines, specifically Google, and I was frustrated with the other keyword research tools (in particular Market Samurai) out there.