The Anti-Spam Settings (once configured) change so infrequently that I personally don't mind having to add/modify a new RBL/URIBL on three different servers once in a blue-moon. Same goes for the Whitelist, Greylist and SMTP Bypass (and Trusted Senders too). It would be a nice convenience, but not overly critical in day-to-day operations, but for initial setup I can certainly see the appeal of such a feature.
However, our Blacklist and SMTP Blocking changes every day, and updating these on three servers is beyond tedious. It would be a *HUGE* Quality of Life improvement to be able to enter this once and have all Gateways receive those changes. Although if Smartertools were to allow that to be Synchronized or to be Exported/Imported, then I can't imagine it would be much more of an effort to do the all the Security Settings.
I imagine this would have to be a toggle setting though as some installations purposely have their Secondary or Tertiary Gateways intentionally set to far stricter Spam Settings as Spammers will skip the Primary MX Record and go directly to the backups hoping to circumvent Spam Filters.