On recent visit to Southwest Utah I saw lots of pygmy forests containing pinyon pines and small oak trees, these forests are sparse and the trees no more than 8-10 feet tall. The National Park literature says that these trees have adapted to low water conditions. Contrast this with the Redwood forests of coastal California where resources (water & sunlight) are abundant. In this environment the trees are more densely packed and grow much taller.
Replace trees with firms and resources for customers, and this paragraph could describe a business landscape. Being binary for a moment, a new firm gets to choose between choosing to enter a market where resources (customers) are slim or to enter a market where there are lots of customers. Choosing a market with few customers, makes it easier to differentiate your firm but the odds of survival are worse. Choosing a market with more customers makes it harder differentiate your firm and therefore the survival odds are also tough.
Unless of course, your firm is first. In both instances you get to choose the best position and consume all available resources.