  We compare the most common SV models such as the Ornstein-Uhlenbeck (OU), the
Heston and the exponential OU (expOU) models. We try to decide which is the
most appropriate one by studying their volatility autocorrelation and leverage
effect, and thus outline the limitations of each model. We add empirical
research on market indices confirming the universality of the leverage and
volatility correlations.
