You are asking, 'Is the concept of soul mates more useful...

You are asking, 'Is the concept of soul mates more useful than marriage?' Concepts don't matter. What matters is your understanding. You can change the word marriage to the word soul mates, but you are the same. You will make the same hell out of soul mates as you have been making out of marriage - nothing has changed, only the word, the label. Don't believe in labels too much.