One duplex or two SFR?

[Blair Boan]

Simple question that has been nagging at me.  Im sure there are multiple caveats to the question but I will try and keep it simple.  

Why do most investors say that the money is in multi family?

Example:

I have an opportunity to purchase a duplex, great location, decent return, 18%.  Or I could simply pick two single family homes from the list that return the same rate of 18%.  Obviously the initial thought is replacing one roof rather than two, but other than that, in my opinion, the two single family homes have a better chance of appreciating quicker if I decided to sell down the road.  

So did I answer my own question? Duplexes are for your long term buy and hold (10 years or more) where as SFR are quicker turnover once that market gets hot?

Thanks in advance.  If I need to throw out any specific details, please let me know.