ninja edit: THIS IS FOR PC GUY 
AA can be controlled by Scalability. Perhaps this is what is happening?
You can put something like this in your scalability ini
[AntiAliasingQuality@0]
r.PostProcessAAQuality=0
r.MSAA.CompositingSampleCount=1
r.MSAACount=1
[AntiAliasingQuality@1]
r.PostProcessAAQuality=2
r.MSAA.CompositingSampleCount=2
r.MSAACount=2
[AntiAliasingQuality@2]
r.PostProcessAAQuality=3
r.MSAA.CompositingSampleCount=4
r.MSAACount=4
[AntiAliasingQuality@3]
r.PostProcessAAQuality=4
r.MSAA.CompositingSampleCount=8
r.MSAACount=8
If you then call r.MSAACount=1 you can toggle between Temporal and MSAA, and use scalability to set the level.
Its great here on Vive. These settings may not be 100% though.
My personal favorite setting is just MSAA of 2x and r.screenpercentage 160
That will give you nice looking UMG and 3D.
I find it runs better than 4x MSAA at 140 percent…