What I have discovered is that it doesn't matter. There's room for lots of companies. All things equal, you want to be the best (which is my shorthand for "stand out from each other in a positive way for the customer's context"). But many customers just want to solve their problem, and don't care about solving their problem in the optimal manner.
As hackers, we're obsessed with the idea that the best solution wins. As an entrepreneur, I've discovered that second rate products with first rate sales and marketing will likely outshine a better product that has outreach as a secondary priority.
This used to upset me, because I was focused on the product. As someone trying to run a business, I'm looking at the company as a whole. That means that sales, marketing, product, support, organization, strategy, vision... they're just 1 component of the whole.
It makes the sales side easier if the product is unique or clearly the best. --
Back to the original point -- companies don't need to stand out from each other when they are the only solution a customer has heard of.
Imagine you are a sandwich shop. When you started, you could just send your marketing by BCCing people through your gmail. Now your list is 2500 people, and you need a way to send to everyone.
You just want to send your email to 2500 people. You don't want to spend a day to compare the relative merits of mailchimp versus constant contact.
Flip the perspective (mailchimp's perspective, looking at the sandwich shop owner). Mailchimp's challenge isn't to differentiate from constant contact, but to simply communicate that they exist and can solve an existing problem.
--
This may be more relevant for b2b versus b2c. I confess I do not understand marketing in b2c much at all.