You have to fetch case studies to convince the client technically (bitter truth, whatever is successful has its cost).   Now the new era began - NGFW comes to the picture AI/ML-based only data sheets, then case studies only the key   Every security appliance has its own cons…

Pick a product model for both vendors: Cisco & Palo Alto (refer to technical data sheets and whitepapers --)  See the key differences on your target or specific needs) Practical evaluation by a person who has both products under the belt and can share their experiences...…

NAT Is always good for security concerns as to some extent it hides internal Networks.  SIP can be used with port forwarding too (it works ) Here I mean SIP (Session Initiation Protocol in VoIP Phones).   Also, I suggest you refer to your firewall docs.  

@Lindsay Mieth Which Model idle Suite for 500 Ssl vpn (Budget alsa a  Considerable Factor ) 

@Mike Hancock yes you are right waht you say on 200F  lient Need to consider Budget too  (Earlier Fortinet Claims 100F Supports 500 SSL Vpn) Now they Promoting 200F for 500 As Per Data Sheet