There's a lot of discussion of this issue on the Navitron forum. From my failing memory:
(1) yes it depends on the occupants usage, because
(2) a thermal store is better for the reasons given by Peter Bayer
(3) and stratification is valuable so
(4) the auxiliary heating should be towards the top of the tank and designed to heat just enough water for one period's use if the solar hasn't done enough
(5) while the solar should have access to the entire tank, but heating from the top first as Peter Starck suggests
(6) BTW, one possibility to avoid is the idea of an auxiliary post-heater fed from the thermal store as a pre-heater, since that doesn't heat the water long enough to kill bacteria reliably.
PS Sorry about not being called Peter, but I guess David is the second best choice