There are many facets to the decision. With investing in mind, is your investment objective to create an income stream, a tax benefit from rental expenses, or a capital benefit from property appreciation? Another consideration is the management and maintenance of the investment.
If it is a matter of an income stream, consider the potential of commercial property with established leases. This provides for the income stream, and will possibly be easier to service and manage. If residential is chosen, managing the properties has a different flavor but is doable. Both have similar tax benefits though the commercial may be easier to establish as a "business venture" with greater potential write-offs....check with your tax guru on this.
If your goal is obtaining a capital benefit from property appreciation, consider a diverse approach. For residential, each location has some unique dynamics:for example South Tampa is school zone driven for residential, commercial is all about access and which side of Kennedy you are on. Each of the markets, residential and commercial, have their cycles. For capital apprciation, buying low and selling high is the mantra. Some areas for residential have already passed their low and are climbing, commercial would depend on the sector and you would want to consult with a commercial agent. There is a commercial division in our office....
Hope this gives you some additional thoughts and options!