Anniebach As someone else said, it would be virtually impossible to have two candidates with exactly the same qualifications, experience and ability to articulate in writing their strengths and weaknesses.
However, I say for about the tenth time, that, in the course of a piece of research relating to employment, an experiment was carried out whereby "imaginary" applicants applied for jobs that had been advertised. Researchers sent out two cvs in response -both identical in their contents, except for their surname. One cv had a typically English surname and the other had an obviously non-European surname. Despite the fact that in every other respect the cvs were identical, the applicants with the English surname were called back for interview at almost twice the rate as those with the non-European surnames.
I expect there may be difficulties determining which of two excellent applicants should be offered a job. However, that does not detract from the fact that there is proven bias towards candidates who are perceived to be white Europeans. It cannot be mere coincidence that one group receives an invitation for interview at almost twice the rate of the other group.
When it comes to the subject of who is successful at interview, that is a bit more tricky but, as Madgran says, an interviewer or panel of interviewers should have a properly laid down procedure to ensure that each candidate is asked the same questions and is assessed according to set criteria.
Anyway, if you routinely have far less chance of being called for interview, you obviously have far less chance of getting the jobs you apply for, however good or bad your interview technique might be.