I'm still troubled by a rather basic question, namely when is a perfect fit to the vanilla skew really necessary?
I think if you are trading vanilla options and/or Europeans that can in theory be perfectly replicated by vanillas (obviously) a `perfect' fit to the vanilla skew is desirable.
Other than that I'm not so sure there is an indisputable reason to have a model (read SLV) that gives a perfect fit? Especially for instance for more exotic products with exposure mainly to forward / future vol.
Is there a way to quantify my vagueness above?