I'm not sure about S20 but I buy the highest end Galaxy S every year ( since the very first ) and although I'm now using S21 Ultra, I still have ( until Friday ) and have had S20 Ultra ( exynos ) since March 2020 and it was good from day 1, but after a few updates it got great, and then after the U.I 3.0 update it got really good. so although S20 has a smaller battery, it also has smaller screen, so is probably pretty good on battery life. I also never experienced any overheating issues at all. of all the Samsung phones inhave had, every year, the last 2 ( S20 Ultra and S21 Ultra ) are absolute power house phones and really good on battery life. Daily i achieved 8+ hours SoT with 10-15% at 60hz WQHD+. I haven't been using it all day for weeks it I would of had screen shots to show you. that being said, S21 is definitely a better option, providing the no expandable storage and WQHD+ doesn't matter to you.