Most people go straight to the most known brands when they are have plan to buy tankless water heater. They skip the customers reviews on many site and go blindly on home appliance expo or local shop near their place and pick it with closed eyes.
That is not wrong at all, because they are trusted brand and they always stay behind their product quality for every item their sell. Of course the price will be higher and spare parts is always ready every time they are need it.
But that also not completely right. Ask them here.
Many people share problem at online forums about their big brand tankless water heater product. They got problem, need service, not properly work, leaked and many things. This mean not all product good, lots of types fail and just few of them is gems. You need to get that gems type to make sure you are have a good product. Since this device will be with you for more than 5 years. Of course you want to use it every time you want, with maintenance cost as little as possible. Not got many problem during daily uses and more more good things that you expect when you decide to get one of them.
And the key, and most important step is choose the right device.