Well, true that investors will ask how well you can capture the market you are targeting. However, what that really boils down to is whether or not the investors believe you can execute well. Actually, sometimes investors will throw more money at you if they think it is a competitive market but believe that you can become the market leader first. After that, if you do well at building a good brand, then you'll get customers based on that, regardless of the competition that pops up.