USP is overused in many circles - and with different definitions.
Wikipedia uses the definition penned by Reeves in "Reality in Advertising" as:
- Each advertisement must make a proposition to the consumer. Not just
words, not just product puffery, not just show-window advertising.
Each advertisement must say to each reader: "Buy this product, and
you will get this specific benefit." The proposition must be one
that the competition either cannot, or does not, offer.
- It must be unique — either a uniqueness of the brand or a claim not
otherwise made in that particular field of advertising.
- The proposition must be so strong that it can move the mass millions,
i.e., pull over new customers to your product
The battle is not between startups but between your defined target market, their price anchors, and the alternatives they use to address the problem / condition you assume that they have. How many members in the target market have you interviewed? Discussed / validated the problem and their desire to address it? Their willingness to pay for the "solution" you offer?
The natural outcome of this effort is your USP (or a pivot towards finding a lucrative USP).
While its not easy to do, the nice thing is - all this can be done before ever writing a single line of code: which would likely be easier (and cheaper) than trying to convince someone to use a service that doesn't meet their needs.