I think they are both important to our lives. But if I can only choose one, I think water is more useful in our daily life. As we all know ,water is the source of life and the link that binds all living beings on this planet. So we cannot live without water. All living creatures need water so that they can grow up smoothly. Our human beings need water everyday, both in our life and work. Compared with water,electrivity came into being later. Water comes first on the earth.
Next I want to say is that imagine the life without electricity, our life won't be colorful, at night we will live in the dark. But, imagine the life without water, we cannot even guard our basic need of live. Because we can bo nothing. You won't cook, the factory will stop work, people's live will be end.
So water is more useful, don't forget to protect the water resourse on the earth.