depends if you want to make money with it. To know the market and the other products helps you to get a better feel of what you could improve
general rule is:
and usually 2 out of 3 are enough.
And we could go on about market positioning, add campaigns, ROI ....
in short it's always good to know your enemy ... :) maybe you can actually create a synergy with one of your competitors? .... knowing more is often better.