We made this change to Admin for several reasons.
1. We needed to remove frame(iframes) based layout from the design to get 508 compliance.
2. We wanted a 100% responsive layout that would work on Phones, Tablets, and computers of all sizes.
3. We wanted to attempt for the user to not have to scroll vertically for navigation. To do that, we needed all of the vertical space available.
4. We wanted every page in our app to be addressable with a simple URL. The in page frames obfuscate the actual URL you are on. Having addressable URLs will allow us to send you a link in an email, feed post, or word document that may outline how to perform certain functions within TeamDynamix.
5. We wanted an app that worked well with all types of touch based screens.
In the end, we are investigating moving all new apps to this type of model. This also helps us with our mobile and native windows app strategy.