If the cylinder is located far away from the tap, and the boiler is close to the tap, and that particular tap is used often, then the combi outlet is better as the hot water will arrive at the tap much quicker and the amount of hot water left in the pipes will be small.In this configuration, which is more efficient, to have the CH flow from a cylinder or direct from the Combi. ?
For that it makes very little difference, because unlike turning a hot tap on briefly many times a day, the cylinder will be heated only once or a few times for an extended period, and the amount of hot water left in the pipes is insignificant compared to the total energy put into the cylinder.getting the boiler right next to the cylinder might be a bit tight
Cylinder location relative to the hot water outlets is far more significant, and all of the pipework should be properly insulated in all cases.