@Needllchelp
I think the ultimate point here is that forming a business or an LLC or a corporation is a legal question that should be answered first, before you worry about how to file your taxes. While it will be easier to file their taxes if the husband and the wife have separate single member LLC‘s, that may not be the best business solution for them.
I would suggest that they make the best legal and business decision that fits their situation, and then file taxes accordingly, instead of making the business decision based on what kind of tax form is easier.
