Hydro technology is more than a century old, and well understood. AC
generator technology, ditto. However, modern electronics and inverters
and alternators have changed the game entirely.

The solar community has driven the development and inexpensive mass
manufacture of DC input paralellable grid inertie-able inverters, which
cost less than just the mechanical transmission and speed regulation
required by a 60 Hz ac generator.

The wind turbine community has driven development of rare earth magnet  
permag alternators that are high power, small and efficient even at low
rpm.

Maximum power point control aids both at optimizing efficiency with
varying input.

Small hydro never would have had the sales volume to drive these
technologies at these price levels, but we have been given some amazing
gifts. Use them!