I have to thank Paul B. for the hint, that the Aqua Terra has in fact AR coating (inside only) but again, you can see that the AR coating on the Grand Seiko is more effective. After I received Paul B.'s hint, I had a very close look at both watches once more and I came to the conclusion that the Grand Seiko must have inner and outer anti-reflective coating. Otherwise I cannot explain the difference in AR effectiveness on these two watches.