differences performance in invoke parallel between ExternalReportWSSService and api rest saas

Summary:

ExternalReportWSSService for bip short report versus an integration oic with more call cycle invoke to rest api saas.

Content (required):

hello I could to know that differences in performance and speed of response(in context with more parallel call) between a short bip report(xmlpserver/services/ExternalReportWSSService operation run report) and invoke more rest Api of the saas in an integration(oic) with cycle etc to transform data from there api rest .

this question is due to the difficulty of retrieving data through more calls from api rest than a bip report but we wonder about the performance and speed with many calls to this report via the soap service(ExternalReportWSSService) compared to calling api rest del saas.