Hey, what is it so difficult? You don wanna marry so dont marry. If you wanna know another opinion see if mine is useful for you. Marriage has no meaning. Relationship has meaning. If you don have time for relationship either.... it means you have other more important things in life... you may wish to just get a rent paying room mate with benefits. The wonderful thing about choosing your own path in life is that you then never have to regret, no matter what happens. If you look at the options both of them require sacrifices and both of them have good parts. Therefore it is only up to your private preferences inside. If you get married you hardly can enjoy the benefits of unmarried life and if you are unmarried...it is harder to have the married life benefits. Think, choose, never regret. That is all.
Ah, and another thing - it is important to see that you respect and are fair to the people in your life whatever your choice and life style.