C-f, C-e, C-b, C-a only require one hand. But I see your point.
The best part of evil-mode in Emacs is that I get to use Emacs bindings in insert mode, and then vim keys in normal mode. For instance when writing function signatures, I can hit C-f to easily jump over the closing parenthesis, or C-e to easily jump to the end of line, usually also to skip the closing parenthesis. I'm not sure how you would do that in vim without exiting back into normal mode and using for instance S-a to append at the end of the line.
I'm a long-term emacs user who recently learned vim for fun. Deciding when to exit insert mode has been part of the learning curve.
From insert mode, vim lets you run one command without explicitly switching back to normal mode. :he i_ctrl-o for details. It's very handy for positioning the cursor for more input, for example ctrl-o f)
The best part of evil-mode in Emacs is that I get to use Emacs bindings in insert mode, and then vim keys in normal mode. For instance when writing function signatures, I can hit C-f to easily jump over the closing parenthesis, or C-e to easily jump to the end of line, usually also to skip the closing parenthesis. I'm not sure how you would do that in vim without exiting back into normal mode and using for instance S-a to append at the end of the line.