An accelerator or in-line pump is designed to ensure water circulation and is used more for climate and temperature control e.g. circulators on heat pumps exchangers.
Booster pumps are used to pressurize a water network, e.g., feed a water tower at a XX meters of elevation.
The accelerator is used primarily to increase the speed of the water in the network. It is very difficult to raise the pressure with it, except if it doesn't come equipped with the “usual” accelerator but instead a jacketed, submerged multicellular pump that is installed directly on the pipe. In our case we used the latter with the aim of ensuring water supply to a village, even when there was a lot of upstream draw on the pipe system. We chose that route because we couldn't use a booster—no surface space and located in a flood zone. The biggest difficulty lay in preventing overspeed upstream and not generating a Venturi effect or losing prime through suction of open vents.
Surface booster systems are much more flexible, even if you often have to set up a adjacent storage tank (this might be a good opportunity to do a round of chlorination...)