Depends whether you have a combi boiler or conventional central heating with hot water tank.
Electric probably more efficient if a small household as no need to heat the water tank up for a shower but it will likely need a dedicated electric feed installing. Can have multiple showers with correct cold,water feeds
If a water tank, a thermostatic conventional shower can have a shower pump attached for a much more powerful shower experience but water has to be kept heated. If a multi shower house it needs capacity to supply more than one