The load time that is noticed for Custom View Tiles is due to the fact that the runtime is loading up the Shindig (OpenSocial) container in the background to provide the API proxy and environment details. When you run an HTML Tile, and you are basically dropping the core-v3 feature, but are still using the same Tile framework, but not loading Shindig. (see: https://community.jivesoftware.com/docs/DOC-141800#jive_content_id_Tile_Features ). Currently, there is a mutually exclusive decision to be made regarding loadTimes and proxied access to the APIs. If you need to use the REST APIs, you will need to use the core-v3 feature on your Tile and incur the Shindig delay.
Yuval Twig is aware of this delay and we are looking into ways to speed this up in future releases.
Does this help clarify the current position?
Thanks. The part that I still don't understand is why the HTML widget vs the HTML tile have different behaviors when accessing the REST APIs (why is the HTML Tile limited). While the Custom View tiles might not have a performance issue in the near future, Jive will still limit a page to 2 custom tiles so that might still force us to handle things differently.