I guess it depends partly on your feelings about large amounts of stored water that you then use.
With the more typical large storage tank that you then consume water from you are using 'older' water (think legionella), with the fresh water only passing through the internal coil you won't run this risk.
Interestingly there is a company in Germany (OEG) that sell 'Hygienic tanks' that have a stainless steel corrugated coil (I guess to increase surface area and promote disturbance)
OEG Hygienic tank.
As your cold water passes through the coil it will pick up heat from the tank so you won't be restricted to a short shower!