One of the most important parts of any start-up's pitch is the competition slide. This is where you both define exactly how you plan to attack a market as well as how you position the competition. I think that it is almost impossible to really understand what YOUR business will do and how you will succeed unless you have a thorough understanding of the competitive landscape.
You need to think about competition broadly -- existing solutions to the problem you plan to solve, substitute solutions, start-ups who may be taking a similar approach as you, big companies, small companies, etc. You have to think about all aspects of these competitors -- technology, financial strength, quality of backers, revenues, brand strength, customers, partners, distribution, etc. One or two lines on strengths and weaknesses isn't enough. Try to look at the landscape they way that a customer would -- why would they buy from them? why would they buy from you?
In a business plan presentation, you'll have to abbreviate this to make it succinct. But, be ready with a more detailed analysis early in the diligence process. Most VCs will ask you about competition very early on. Show them that you know your market.
Also, don't be afraid of showing that you have competitors or that there are other start-ups with similar ideas. There are no interesting markets with few competitors. The key is how you will target segments in your market, how you will tailor features and distribution partners to reach that segment, and how your unique insights and combination of skills give you some advantage in that segment. Markets are rarely targeted and won horizontally. So, initial segmentation is important.
As a VC, I was always wary when I started finding competitors that the entrepreneur either didn't know about or didn't know much about. That made me think that they didn't know the market well. And, there will always be smaller competitors that you don't find right away. So, if you can find a few new ones, you can be sure that there are a few more. A good entrepreneur will have their ear to the ground more closely than a VC and should know the landscape well.