Startups can always identify their competition. If they're in a worthwhile market, they have competitors, and they know who they are. Surprisingly, I have found that many startups can't pinpoint the way in which they compete, and many more haven't thought deeply about why they should compete in that particular way.
Startups can compete in three main dimensions; quality, convenience, and price. As startups grow, they gain resources, leverage and market share, which allows them to compete in more ways than one (Airbnb is an example of startup that often beats hotels at all three). However, early stage startups usually only have the ability to compete in one dimension well.It's usually not that difficult to figure out how best to compete, and it's critically important. Knowing the company's key dimension of competition is on the short list of things everyone at a startup should know at any given point (other items on the list include short-term goals and critical metrics).
Intuition and empirical examples typically lead to the same conclusions and should allow founders to extrapolate the best way for their startup to compete.
Quality
From what I've seen, startups often prefer to compete on quality; it's everyone dream to offer a truly better solution than anything else that exists. Marc Andreessen said that to be successful, startups have to offer a solution that is 10X better than existing solutions.
Startups should compete on quality only when they actually have something is that is 10X better than existing solutions. This requires a very honest look at your product and market. Can you really provide users with a product that is so much better than everything else on the market that nothing else matters? If you are, great. If you aren't, that's okay - you can still be successful, you just have to compete differently.
Convenience
Competing on convenience makes sense when two conditions are sufficiently satisfied: 1) demand for a solution is price-inelastic and 2) existing solutions are inconvenient.
Uber is a great example of a startup that competes with other car services on convenience. Uber has been successful because it is so much more convenient than any other transportation solution, not because of cheap prices or unbeatable high quality. People need to get around and they will pay to do it, so competing on convenience makes sense in this market.
Price
Startups can successfully compete on price when one of two conditions is satisfied: either 1) existing market prices are artificially high for some reason, or 2) when offering a solution at a cheaper price will gain sufficient market share to ultimately drive the company's success.
Warby Parker's value proposition and success has come from competing on price, and they have been able to do so because of artificially high market prices. The international conglomerate Luxottica had a stranglehold on the high-end eyewear industry, and was selling glasses for $300-500 that it produced for less than $20. By entering the same supply chains and cutting out middle men and licensers, Warby Parker successfully entered the market based on $95 glasses.
Competing on price is tricky and should be done thoughtfully. Amazon is famous for this strategy; they slashed their margins to almost nothing in order to successfully gain a stranglehold on the online retail and book markets.
Know yourself, know your market
Picking your dimension of competition is critical, and I think a lot of startups would do well to give it more consideration. Knowing exactly why you belong in the market gives your team focus and a sense of purpose that will allow you to increase your value-add to users and ultimately the size of your business.