Hi Prolin
For electrical component, it's very hard to recommend. Sometimes in life, even when you buy the best reputable system it can come up as a lemon. End of the day, your budget might play a very important factor, sometimes, even your usage pattern might change your purchases. Personally I think Dalkin should be one of the best in terms of quality and functionality, but my budget only allows my to go for Mitsubishi. Reason I chose Mitsubishi is due to the feature wise as compare to brands like Toshiba, Panasonic, Sanyo, LG and etc...
Hi Raynard
It depends on your bathing needs. If you are those who needs half an hour of constant "rain", I bet storage heater's water cache will also be drained... moreover, it also depends whether do you need high water temperature??? In Singapore, it's not likely that we need over 60 degree celcius water for bathing, most of the time, all thanks to the heat and sunshine, we basically can bath without turning on water heater. Hahahaha.. of course, some people habits is different from others. So instead of looking which one is more economical, think of which one suits you better.