I’d also say that a deferral at one school is not the same thing as a deferral at another school. For example, Stanford rarely defers its REA applicants, whereas Princeton defers ~80% of its SCEA applicants. Stanford deferrals have a 10-20% chance of acceptance, whereas Princeton deferrals face a 4-5% chance of acceptance.
Moreover, your deferral chances also come down to the applicant. Are your test scores weak? If so, consider raising your test scores to increase your chances. If your grades are low, continue to show an upward trend.