It really depends on the deployment in my opinion.
Whilst the master / master redundancy gives you the ability to continure to be able to make changes to the configuration having a master / local also gives you many advantages.
Double the; firewall throughput, encrypted thoughput, availalbe switchports, max clients, etc.
If you need the resources then master / local makes them available.
... but like I said, it depends on the deployment. :smileyhappy: