I believe Kevin White's answer is partially incorrect (less partially that I origanally thought!, as well as showing N-channel fets). Neither way will work if the gate is not referenced to the floating sources unless the gates can goto the extremes of the signal (because of the diodes). Either way will work with that limitation.

In the common source case then as Kevin points out referencing the gates to the floating source allows switching of positive or negative voltages without limitations of Vgs

[![enter image description here][1]][1]

If the gates are referenced to the left hand side (Common) then it is clear that in the Common-Source case if the Load is more negative, then Vgate must be < than S3/4 which is only one diode drop from Common to turn on and >= Common to turn off. If the Source is more positive, then Vgate must be less than Common to turn on but >= S3/4 which is now one diode drop from Source.

In the Common-Drain case if the Load is more negative, then Vgate must be less than Load to turn on and >= Common to turn off. If the Source is more positive, then Vgate must be < Common to turn on and >= Source to turn off.

Assuming Common can only swing between Load and Source then Vgate has to be able to swing from Source to Load-G(thres) in either configuration. Apart from possibly the fact that in the Common-Drain case the two fets can share a heatsink I can see no reason to recommend it.


  [1]: https://i.sstatic.net/3DTXE.png