The importance of your family needs cannot be underestimated. The whole basis of your quote and installation will balance on these requirements. For instance if you buy an electric water heaters that are too small will have frequent times when the water cools down while in the shower or many other inappropriate times. Conversely having a system that is too large creates an unnecessary financial drain on the household budget through the energy costs associated with maintaining a large hot water storage tank.
A quick look at your home will give you a rough idea as to what you will be needing. For instance, how many bathrooms are in the home, how many members are there in the home, lots of children mean lots of showers, baths and extra clothes washing sessions, and last but not least don´t forget the extra house comforts like the dishwasher. Obviously, a couple living in a large house or a large family living in a small home will not require anywhere near the same capacity water heater as a large family.
Are electric water heaters better or worse than other forms of hot water systems? Well that is relative to your needs and available energy sources. Someone living in the rural country areas may not have access to gas for example. There are many homes these days that are converting over to solar powered hot water systems to avoid the costly utility bills, although initially the purchase cost is far higher than electric water heaters.
For convenience, electric water heaters are probably the most common overall but this does not mean that they are the right choice for you. As you can see, there are many factors associated to choosing the system that is right for you whether it be tankless, electric, geothermal, solar, gas or oil burning there is no right or wrong, it all depends on what is right for you circumstances, as long as it meets your needs it is the right choice.