These 3 keyword matching options are not solely to blame for the large variations seen when comparing data from the keyword tools. Much of this difference can be attributed to the distinctive techniques that the tools use to collect their data. Let’s take a look at how these tools collect and present their data and hopefully it will help clear up any confusion.

The Google Keyword Tool is SUPER helpful for building a foundation for your keyword research strategy. At the end of the day, these search numbers are coming straight from the horses mouth. You can filter down to a hyper-local level and see which keywords are getting the largest search volume. Plus, with it’s integration with PPC you can get a quick idea about commercial intent by looking at the bid and competition metrics. How much are people bidding on KWs, higher = more likely to generate a return. Usually its aligned with search intent. That said, the trending data is a little less reliable. I would still use Trends to analyze the popularity/ seasonality of KW search volume.

Keywords are supplied with accurate, clickstream-based metrics, some of which are exclusive to Ahrefs. For example, Clicks and Clicks Per Search can give you a better idea of how much traffic your content can get. That’s a burning issue today – many queries never translate into clicks because Google reveals answers for them at the top of SERP (i.e., Knowledge Card).
The limit on manual keywords could be higher.  I personally wish we could input 10,000 keywords at a time, instead of 200.  However, I understand the costs that Long Tail Pro has to maintain each time a new manual keyword is input.  Not a deal breaker, I just wish the limit was higher. (To be fair, I don't think most keyword tools have a bulk manual option at all).