Android: Poor Performance w/ Large Images

I'm working on a App (not a game!) built with Unity, and it consists of a number of full screen panels.

Testing with a 2013 Android Nexus 7, I've noticed that performance drops extremely quickly as I stack full screen images. I think this is somewhat related to a poor fill rate on the Nexus 7, but uGUI shows much worse performance than Sprite Renderers.

I made a test scene, where I stack a bunch of fullscreen images on top of eachother, and compare the performance of ugui's Image vs...

Android: Poor Performance w/ Large Images