To get a feel for how graphics performance on the Galaxy S6 and S6 Edge compare to other devices, we used GFXBench, which has been one of our standard graphics performance benchmarks for a while. In order to ensure Vsynch and resolution isn’t a limiting factor, we will compare offscreen test results. We also used Futuremark's 3DMark Ice Storm Unlimited benchmark.
Here's where things got a little strange. The HTC One M9 has a Snapdragon 810 and Adreno GPU, while Samsung is pairing a Mali GPU with its octa-core processor arrangement. Based on these scores, it appears that the Snapdragon + Adreno combination is still superior when it comes to GPU performance. While the Galaxy S6 outperformed the M9 in all of the general performance benchmarks on the prior page, the M9 routinely bested the S6 duo when it came to gaming. If you compared the S6 to the S6 from last year, you'll see a healthy and sizable gain. But if you compare to the Adreno-based M9, there's a notable gap.
This Ice Storm Unlimited test places a significant amount of sustained strain on a phone's CPU and GPU, and once again, we see the S6 units fall behind the M9. For what it's worth, gaming on both S6 units was perfectly fine, so the performance is there. We watched the tests themselves, and never saw a hint of lag or stuttering, and in fact, neither phone ever became uncomfortably warm during the benchmarks.