Unsure of what to get 📱

So I'm stuck between the Samsung Galaxy A57 or a Samsung Galaxy S26 Ultra, I'm looking to upgrade as my current phone as it has some lines on on the screen, i currently have the Galaxy s21fe and I'm in need of an upgrade, either I can outright buy the Samsung A57 or I can get the Samsung Galaxy ultra S26 on an O2 contract for the next two years, what should I get?