First of all the term 'vectorizing' is a misnomer. There's no such thing. The process is edge tracing. Since there is no vector information in a bitmap, at least yet but it might be possible, what everyone calls vectorizing really is nothing more than examining a bitmap and detecting, in the sole opinion of whatever or whomever is doing the detecting, edges. This is totally subjective, there is no objectivity here. You look at a bitmap and discern that various discrete pierces that might construe vector objects. An algorithm does it a bit differently, it looks for acute color changes to determine where edges might be. Nonetheless, it's every bit as subjective as you eyeballing the image and tracing what you think ought to be edges.
Some alforithms are better at it than others but they all do it the same way. I like the trace facility in Corel 18, a vast improvement over previous editions. Flexi is rather primitive. Adobe is about the same as Corel. There are a number of online facilities that do a decent job as well. Whatever you use unless the bitmap is high resolution and crisp, you'll have to manually tweak the results. The better the image the less tweaking.
Moreover, the notion of creating a bitmap from a vector image and then tracing the bitmap to reproduce the original vector image is a non-starter. What you will get is only an approximation of the original vector image. With arbitrary objects close usually will work but text is another story. An approximation of most type faces is less than acceptable. Best to re set any text rather than use the tracing results.
