Switching from iPhone

Hi guys, I wanted to get your opinion, I have iPhone 15 pro and was thinking of switching to the S25 ultra, I am just an ordinary not a power user but I hate my iPhone so much since the latest iOS 18 updates, my last Samsung was A50 which was glitchy and laggy, i know it’s mid range but I have some questions:

1)do the flagships get laggy after a while?

2)If anyone was in my spot and did the switch what does he think?

3)In terms of privacy and security, I have my whole life including government and bank apps on my iPhone, are Samsung phones secure?

Thanks in advance.