Lessee here...I just pulled out my copy of 'Superman Beyond 3D' #2 which I had bought based on my arguments with people over the 'greatness' of this tie-in, just to see if I was missing something.
From a fashion perspective, there is absolutely no doubt the cosmic armor defeats the IG. It is really spiffy, while the IG ABSOLUTELY SCREAMS "uh, the 1970's called! They want their color scheme back!"
Functionality? Here is where the CA gets the big 👇
CA Supes meets Mandrakk on page 25 of issue 2.
Page #25 - Mandrakk blasts Superman with, uh, 'Evil-Vision'. Superman fires back with heat-vision. Mandrakk then tries to electrocute Supes.
Page #26 - More Evil-Vision and lightening from Mandrakk.
Page #27 - Lotsa chitty-chat
Page #28 - Supes gets pissed and delivers a bag-shot (dirty cheater!)
Page #28 - More chitty-chat
Page #29 - Supes grabs a piece of rebar and stakes that damn dirty vampire. One final blast of heat-vision sends Mandrakk into the abyss, 'until even the idea of him is lost'...'until the Overvoid, the mind of the Monitor, engulfs him...already forgetting' (that is until Mandrakk reappears 4 pages later drylaugh)
Based on the above epic/titillating battle of CA Supes I would choose to wield the IG any day of the week.