Five Small Residential Multis or One 15-20 Unit Apartment Building?

[Tim Porsche]

This question is for those of you who own, or have owned both small residential multi units (2-4 doors) and larger commercial apartment buildings (4+ doors). Would you rather purchase five small residential multi unit rentals, or purchase a single apartment building that contains somewhere between 15-20 units?

I know there are obviously a lot of pros and cons to each, but I'm curious which you would choose, and why? I currently have two single family homes, and three small residential multi unit buildings as rentals. I'm debating if I should continue to purchase small residential properties over the next several years until I reach 10 residential rental properties, or wait and save up for several years, and buy one larger building instead. 

Part of my likes the simplicity of only having to deal with one water/sewer bill, one trash bill, one township for yearly inspections, one insurance company, one roof to replace, etc. As well as only going through the process of finding, financing, purchasing, and stabilizing one property vs five. I would probably put the money used to save for a larger building in an S&P 500 index fund, and only withdraw when the market is up. As I'm not in a rush, I would be okay waiting a few years for the market to recover if it happens to be down when I'm ready to start looking for a small apartment building. 

On the other hand, there are a lot of advantages to owning several smaller residential multi-units, like cheaper and easier financing, smaller down payment required for each, diversification with multiple properties in different areas, easier to sell eventually, etc. So for you personally, what would you prefer and why? Thanks in advance for any advice!