The Google Keyword Tool has a variety of helpful features meant to streamline the keyword research process. By entering terms or phrases into the search box, the Keyword Tool allows you to build extensive, relevant keyword lists from one simple interface. By default, the tool displays Advertising Competition, Global Monthly Searches, Local Monthly Searches, and Local Search Trends for each keyword. Additional options allow marketers to show the estimated Average Cost per Click, Ad share, and Search Share.
Long Tail Pro helps to assess the strength of your competition and put you ahead of your competitors. It would help you to rank higher than your competitors. When it fetches the keywords for you, it filters it and delivers the relevant ones after filtering them and making them relevant to your domain. This way it would help place your business and your website ahead of its competitors.
I just have the free version right now so I don't know all that the pro one can do. But even the free version has A LOT of tools you can use, I haven't even figured them all out yet. But one that I have used is their Content Optimizer. You can take a new or existing content piece of yours, and compare it to one of your competitor's pieces on a similar topic, and see where you might be lacking based on the keywords that are used in each piece.
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.
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).