For comfort, for saving water, and for saving energy, the best possible solution is to minimize the amount of water between your fixtures and water heater. Simple as that. The lower the volume of water between the heater and fixture, the sooner you get hot water when you turn on the tap (comfort), the less water that flows down the drain while waiting (saving water), and the less water that sits and cools in the line after you turn off the tap (saving energy). To this end, locating the water heater centrally in the house and as close as possible to the fixtures is critical. Parallel piping manifold systems reduce the water volume as well. Parallel piping systems have home run lines from a manifold to each fixture and use much smaller lines (for sinks, 3/8" lines for sinks instead of a combination of 3/4" and 1/2" lines). There are 11.00 cups of water per 30' of 3/4" ID line, 4.89 cups per 30' of 1/2" ID line, and 2.75 cups per 30' of 3/8" ID line, a significant difference. In other words, you can see hot water 2 to 4 times as fast with a parallel piping system versus a conventional branch system.
There are a few other benefits as well. One, no pressure balance issues. You can flush the toilet while the love of your life is in the shower and they will not see the slightest temperature dip or spike. Two, there are few if any fittings on the home runs so the system is more durable and the flow is smoother and faster (less turbulence) in the pipes. Lastly, you can turn off any line at the manifold so maintenance and repair just got easier.