SFR vs. Multi - there are many investors that swear by and stick to both categories. The general arguments for SFR's that I'm familiar with are -
-better appreciation when things are actually appreciating
-they are the bread and butter of the RE market, so easier to move them if you want to free up some capital
-different quality of tenant that will tend to think of the property more as their home than a temporary residence - if the tenants have kids and pets and accumulate all the junk that one tends to when one has the space to spare, less likely to just pick up and move on a whim
-exponentially more SFR's than larger multis, hence many more motivated sellers who will be open to investor-level offers
-possible to convert tenants into lease option buyers if you want to use that as an exit strategy
Yes, one tenant leaving a SFR = 100% vacancy, but one really bad tenant in a multi can also result in several tenants leaving - which won't happen in a SFR.
There are convincing arguments in every camp.