Unity UI VS Native UI

So at a previous job I worked at, we used unity and we originally used UGUI for all our UI for mobile apps. But we eventually switched to setting up all the UI within Xcode and Android studio and doing calls to unity through native Objective C and Java. They were very strict in not letting us do any UI within Unity unless it needed to be in the 3D space like hotspots etc. all UI must be on the native side of the device used. They said the reason for this was performance and UI done natively doing callbacks to unity was far more efficient and responsive. Is this true? I've tried finding resources and proof of this online but from what I could find, literally nobody is talking about this method. I was unable to test it out myself as I was simply an artist at the company and did not work on development or see the possible improvements or differences first hand.

Does anyone have any further insight into this? I would like to know for the project I'm working on currently if I should build my UI natively or just use UGUI if I want to get the most responsive UI I can. My UI will also have a lot of animation in it.
Thanks in advance for any opinions/insight.

 

You can definetely use UGUI. With the help of plugin like Woo Panels you can create complex UI menus which will be easy to navigate and automatically managed for you by the plugin. Here is the forum thread.

 

I am interested in develop unity with Native UI, is there any tutorial or project about how to create complex native ui with Unity ? or how can i distinguish native ui and unity ui when i launch a app ?