The exynos S9 seems higher than other android phones on geekbench 4 for some reason. I don't personally own the exynos version of the S9 to make a comparison. A11 should be faster based on what I've read, but the iphone X's biggest weakness is the RAM management. I never liked it as iphone 7 on IOS 10 had great RAM management, and to go from there to the poor RAM management on the more expensive iphone X was disappointing. I do hope IOS 12 cleans this up.
No Apple fan can deny bad RAM management on iOS but it’s due to smaller amount of RAM too not so much bad management.
Notice how A11 beats Exynos hands down when opening apps? It’s not till the tail end when you need more ram to hold open all these apps is where it gets beat, it’s not because the CPU is slower but because there’s a smaller space to hold them all open and it has to reload the info.
So the argument of which is faster and more energy efficient chip, is the A11 .