@Susan W. I think that is a pretty easy answer. Multifamily will outperform single family in a downturn most every time. The reason is that single family is more emotionally based and the values are a result of comparable properties in the area when it comes to pricing. Multifamily is run more as a business and therefore the prices are reflective of the performance of the business. There is no emotion to it or at least there shouldn't be. It is simply a numbers game and the better the business performs, the more value that is attached to the property. There are also great advantages to the scalability, especially in larger multi. In addition, there is a huge advantage with respect to affordability, as well as having multiple doors under one roof when people move out or rents are reduced.
I would encourage you to research the great recession and compare the number of foreclosures. Single family as we all know was decimated during this time but multi help fairly well. Granted- every recession is different, so maybe I will eat crow this time! Multi is definitely not recession proof but the asset class typically performs much better than most asset classes in real estate.