Mmm, don't know if it is a real improvement. Looks a bit "too clean" to me. The left image has more "authenticity" to it. Seems like the old ink has bleeded a bit. You also lost a bit of detail with vectorizing the image. Look at the eye for instance: in the unvectored image it has two white spots, a big one and a small one. The small one got lost during the vectoring process. Idem for the curves at the bottom of the nose. The subtle "weave" there is lost too.
I also experimented with software like VectorMagic, but sometimes the unvectorized image still is better than the vectorized one in the end...
Just my two cents...