We can find many reasons why people who theoretically can qualify using I-864 get issues using them in practice. Subjectively, by observing VJ posts for a while I can conclude that pursuing joint sponsor may be a path of least resistance, otherwise we wouldn't see this many posts of applicants struggling with I-864 when using assets. We can give a green light to somebody who appears to qualify to only find later they lost 3-6 months dealing with RFEs or NOIDs based on intricate technicalities. Adjudicators selectively close eyes in one set of cases and are super maticulous in other cases when it comes to using assets. When something works half of the time, my recommendation is to pick something more robust.
In marriage, we can choose the other half. We can date, chat, live together and learn about the person before committing. We cannot pick adjudicator who decides whether I-864 with assets is accepted, so I wouldn't compare it