My opinion - there are equal chances of rejection/approval. RPRF request should not be used to gauge success/failure of an application.
Before (a few years ago) getting an RPRF request was a somewhat accurate indicator that all is well on your application. This is because the request was observed to be sent near the end of the application process, and was observed to be a pre-cursor to issuance of a visa.
This is not a valid observation anymore - as it is observed in the past few years, the RPRF may be requested mid-process, even while medical/security/criminality and/or other eligibility checks are being done concurrently, and pending results. Triggering an RPRF request has been observed as not dependent on the results/sequential after completion of the admissibility checks. So there exists the more common scenario of the RPRF requested and paid for, but the applicant can be rejected based on the results of medical/criminality/security/other eligibility assessments.
.../hth
RPRF usually is requested after medical results have been received by the visa office. In my case, RPRF is requested 2 months after received my medical results. So I'm assuming they already did all the background/criminal checks right? Thanks!