Dear Home Buyer in Salt Lake City,
This question always depends on personal preference. You already own a 4-Plex, so you are savvy to the fact that it bring you equity in the future with renting out the units that are not used by family/friends. In fact all real estate brings equity (even in a down market) if you can wait for your investment to mature.
The question is, what are your personal needs, are you thinking of another 4 plex, for additional income or are you thinking of privacy for your family in the future once your son is no longer in the home and your family will be occupying it? or a Condo where you have no yard work. That is why I say personal preference. You alone can make that decision. Your Real Estate Professional can guide you in the market but ultimately it is your final decision.