Hi Labron,
Switches are really a personal preference thing, either of these two solutions are fine. With the failsafe switch you have one, small switch that turns both batteries on/off. The down side is that there is still a very small current drain on the batteries when the system is off (~5mA/day per battery). With the mechanical switches you do not have the current draw when the system is off but you have two bigger switches mount in the plane with more wiring.