Before revision:  it is able to accurately capture the joint dynamics of equity and VIX derivatives, without sacrificing analytic tractability. The model produces a good short-term fit to the implied volatility of index options due to the richer dynamics, while retaining the analytic tractability of its pure-diffusion counterpart .
After revision:  it is able to accurately capture the joint dynamics of equity and VIX derivatives, but accurately captures the smile in implied volatilities of short-term index options .