Query on using RFC or proxy

Hi,

I have a scenario which is from SAP to PI to Legacy. The legacy system is giving a wsdl file.And from SAP we have a standard BAPI available. I am thinking of going for a RFC-PI- SOAP scenario. But there are discussions going on to use Proxy. Please let me know which would be the feasible option using RFC or proxy at the sender.IT is a synchronus

Thanks