Hello Luis,
I think the ASA would be your best option, firewalling talking is awesome and so flexible. Then it provide you tools that are unique for troubleshooting purposes ( Packet-tracer as an example) Now on the routing side it can integrate really well in a routing desing . So I will go on that road.
Of course with a router you will be able to do differente things like build DMVPN or GETVPNS, and you will support more routing protocols but the Firewall is not as flexible as the ASA. Of course the ZBFW is really flexible but I would say "playing with the ASA is easier than the Zone-based firewall router" as the ASA was designed to be a security device
Regards,
Julio
Julio Carvajal
Senior Network Security and Core Specialist
CCIE #42930, 2xCCNP, JNCIP-SEC