The first Galaxy S21 Ultra comparative benchmarks suggested the Snapdragon 888 might still have the edge over Exynos 2100 when it comes to power efficiency but a new video suggests there's more to the story. The 30-minute battery test itself is separated into several stages and some of them include stress tests and performance tests. At the end of the video, the Exynos 2100 ends up better in preserving the battery. The margin is only 2%, suggesting it will barely be perceivable in real life usage, though. Plus phone batteries sometimes drop unevenly, so the result might have been...
Source: https://www.gsmarena.com/exynos_2100_edges_out_the_snapdragon_888_in_a_battery_test_with_galaxy_s21_ultra-news-47542.php