Marriage vs. cohabitation (relationship wise) which is best to you and why?

Around the friendly neighborhood round table the debate goes on marriage vs. cohabitation (like marriage but not really married). With marriage the plus is you have inheritance, rights and end of life decisions by default, etc. With cohabitation you you don’t have to by a gown or pay for a wedding etc.

What is your choice and the pros you see in it as oppose to the other? And please do not be lazy and just say “Marriage is just a piece of paper”, or “cohabitation is a sin” make the case, act as if there was money on the line.