[Serusers] Using Asterisk as mediagateway with or without rtpproxy

Hi again :) Got one more question about using a mediagateway. Right now I've got everything configured that SER relays the call to our mediagateway (asterisk) when necessary. The mediagateway is also on a public IP, but only accepting UDP port 5060 connections from the SER proxy. (We use RP (reverse path) filtering on our routers, so the IP address cannot be spoofed). Come to think of it, I can additionally also filter on MAC address since both machines are in the same LAN.. I read that a lot of people use an RTP proxy for forwarding the RTP traffic to the gateway (which in turn is in a private net). My question is: Is my setup less secure than using the RTP proxy ? If so, why ? Thanks ! Regards, Leon