SwiftKey keyboard best for prediction and auto correct, password..also in web browser also corrects mistake.
Swiftkey theme's are crap and old fashioned, out dated.
Gborad has more modern theme's, looks alot better, has good auto correct. voice to text seem's better i think.
Gboard in web browser don't want to auto correct. also if you have secure folder enabled then you can't sync back up your data.
Samsung Keyboard is ok for most people, i like color change with theme. don't like the auto-correct that much.