The Snapdragon 810 will be Qualcomm's first generation 64 bit processor, and in doing so the cpu cores are standard ARM Cortex A57 (high performance) and and Cortex A53 (better battery life). If Samsung uses their own 64 bit processor, the cpu cores will be the exact same CortexA57 and Cortex A53, but just a different gpu.
Past Snapdragon 32bit processors (805, 801, 800, etc) used Qualcomm's own custom designed Krait cpu core which were better in real world use than the standard Cortex A15 (high performance) and Cortex A7 (better battery life). That's why Snapdragon processors were better on the cpu side than those 8 core Exynos and whatever Nvidia had with their 8 core design, as those 8 core processors were constantly trying to adjust load with battery life with the different cpus cores. Until we see modified 64 bit cpu cores from Qualcomm and not the standard ARM cpu cores I would expect cpu performance to be roughly the same with Exynos, but there will be differences in gpu.
The Exynos used in the Note 4 in some international markets were still 32 bit versions, but if Samsung uses their own Exynos in this year's flagships expect the 64 bit versions.
