While the peak performance seems to be more or less the same, the AMD mRDNA 2 chip is reportedly better than the current Exynos implementation when it comes to throttling.
In the first round of testing, the performance of the mobile RDNA 2 GPU drops by about 20% from peak followed by another 10% drop in the second round for a total of 30%.The interesting part is that, despite the 30% loss in performance due to throttling, AMD's mobile Radeon RDNA 2 GPU is still faster than the latest Mali GPU; we presume it is the Mali-G78 being referenced here.
The rumor of which mRDNA2 is set to be equipped in the next Exynos is overwhelming the competitor chip in peak performance, according to an actual performance test