Bernie,
Our current setup is similar to the one you described. We also use GeoCortex/VertiGIS. The reason I'm looking at AGOL and or Portal is that I see it as a much better and more flexible solution (not to mention we're paying ESRI a lot of money to use these systems and I want to make better use of them). Here is a list of advantages that I see to using AGOL and or Portal over just an ArcGIS Server:
Flexibility – easy to share data to anyone anywhere
Feature Layers or hosted tables are easy to share for integration into other enterprise-like systems like Cityworks, IT Pipes, Accela or others.
Easy to do metadata / documentation
Easy to setup and manage permissions, licenses, groups, and users
Easy setup for mobile data use and updates
Easy to create maps and apps for whatever use.
Easy to make your data and maps available for use on various devices like website, smartphones, tablets, ArcGIS Pro
Easy to see stats and other information like: when was the layer created, when was the layer last updated, how many views as it gotten
Editor tracking will show the actual username of who edited the data, rather than “ESRI Anonymous”.
Availability will be very high – better than our local ArcGIS Server
Don’t have to worry about internal software upgrades to Windows or ArcGIS Server that could affect the data availability.
The apps and maps should work faster.
Makes us less dependent on our Network team. In other words, we have more control of our stuff.
