From the point of view of efficiency, solar heaters beat pv. With pv you need to convert the sun's energy into electrical energy, with losses, then convert electrical energy into heat by extracting it from the outside with the heat pump. If you store it in batteries to heat up water later, there's even more losses. Depending on the outside temperature, there's a limit to what the heat pump can do, which an internal electric heater inside the water tank takes over to reach usable shower temperature.

With solar heating the sun heats water, that's it. Not only you can yield energy from the sun more efficiently, this doesn't need complex electronics or semiconductors, so it's also better from an environmental impact point of view.

And it doesn't have to be either/or. In my country, solar heating usually comes as a package deal with pv heating. Some companies are making hybrid pvs. Solar panels become less efficient as they heat up, so a hybrid pv would use coolant to keep them within their most efficient working temperature and extract that heat to be used for space heating, using radiators or floor heating or forced air systems, and/or water heating. Having both just makes sense, since it makes your pv needs (and your upfront investment) smaller and the maintenance on solar heaters is much simpler.