A client is looking to upgrade an ancient ArcIMS site, which is quite complex. It has a table of contents, the ability to change symbology on-the-fly, print the map, use spatial bookmarks, identify the "active" layer, export data, etc. It's almost like an online version of ArcView 3.
They wish to upgrade to ArcGIS Server 10, and are seeking recommendations on which of the ArcGIS Server APIs to use.
1) Is there a point of complexity after which the JS API no longer makes sense, and a plugin would offer easier development and better performance?
2) Is it easier to develop a complex application (as described above) using Flex or Silverlight?