@John Warren @Pat L. @Ian Walsh
Thank you all for your replies and valuable opinions. My observation is the same. From renting's perspective, it is the same as multi-family.
Because we already have one mixed use in a decent location, my wife wants to diversify the investment property type. So the next property can sell faster than the mixed use in case we really need the emergency money. We want to be able to sell quick. We think because commercial property requires much more down payment, it will be harder to find the buyers. This is also something we want to avoid when refinancing. (3 units --> commercial = more down payment)
So the take away from this conversation is that the location is the most important factor for mix use. If the location is right, I can sell or rent it quickly.
% of down payment is a different topic though. Should I go above 4+ units or mixed use and pay higher down as opposed to residential multi-family with lower down.
The same money, I can hold on 2 residential MFs versus 1 commercial property.
I don't have the answer. :) I am sure each has its pros and cons.