Rabadon's vs. Ardent censer on a level 3 shen ult

First graph is how much shield each build gets. R=rabadons, A=ardent.

http://i.imgur.com/leHMgGI.png

Second graph is the cost efficiency of the build. (shield/cost of build)

http://i.imgur.com/rQGZT7g.png

This is implying ardent's shield bonus stacks additively, anyway. I mean, it doesn't say UNIQUE, it's just a passive.