HSIM have grow fast in this few years. But starsim and nanosim have a long history. I feel one of the best function in the HSIM is it can directly compatible with spice simulation.
HSIM is the 'whole chip spice netlist simulator'. It speedup traditional spice 1,000~10,000 times(as the company announce), it's a 'fast spice simulator', in addition, it can read test vector(use it's tools covert from *.vcd ) to verify and simplify the test result in the digital parts. With the simulation output results, we can get a delicate current and power estimation. It's important for many IC products.