Power-to-weight ratio yes. But low speed (or high torque)? Last I heard a Tesla turbine has extremely high speed and pretty low torque. (Even one of those web pages is talking 2,000 to 10,000 RPM, which seems a bit low for a Tesla to me.)
(Did I miss something in one of the articles? Other than the low-speed experiment with water to try to track the flow streamlines?)
It's hard to get torque when you're depending entirely on friction of a fluid running along a flat surface to connect the working fluid to the turbine. Teslas run at extreme speed and need little torque to achieve high horsepower.
The reason they're using Teslas is that they're using the solar collector as a boiler. Decently efficient tesla turbines are a snap to construct compared to a vane-style turbine or a piston-style steam engine. They're also small and light.
A high-speed low-torque prime mover makes for a small, cheap, light high-frequency generator, too.
