Do you actually love someone ?
Do you like being with him/her ?
Does that person keeps you happy ?
If the answer to all the three questions above are yes then look no further and go for a committed relationship. I would say it actually doesn’t matter that you go you marriage or live-in if you are with the right person.
What matters is the person with whom you are going to spend your life with if the couple is honest and committed to each other then they will make their relationship a success.
As for marriage and live-in’s are concerned there are pro’s and cons to both of them and there are good and bad examples of couples in both marriages and live-in’s.