I believe Kevin White's answer is incorrect (as well as showing N-channel fets). Either way will work as demonstrated by the original question (presumably his edit).
In the common drain the top fet will always turn on first followed by the bottom fet as the bottom fet's body diode conducts bringing its source higher than its gate. The issue with this configuration is that it is slower (the upper fet has to turn on first) and the supply voltage must be lower than max Vgs (strictly speaking V(Gateoff) - V(gnd) < max Vgs).
In the common source configuration the upper fet's body diode keeps the floating sources at < 1 diode drop from V(supply) and both fets effectively turn on simultaneously.
It is the same for N-channel fets used as a low-side switch - common source is faster and there is no Vgs restriction on Vsupply