Whenever I sculpt a drawing, the relationship between the two practices is always quite striking. I never feel that I need the sculpt to look exactly like the drawing. I'm looking to capture the spirit of the drawing and hopefully improve on the definition of its personality.
When done most of my personal sculpts become references I use for a project either 2d animation or comics. Having a sculpt to refer to for drawing proportions and technical details is great, but more importantly the sculpt is a solid base to build on. The sculpt gives me insight for better visual consistency, weight distribution in my drawings, expression, etc and even aids muscle memory involved in drawing the character. To summarize, the manner in which the two practices inform one another is just a fantastic cycle.