Excellent Quality but poor on speed over time.
Vectorizer.ai is a really good, maybe the best website / service for converting raster to vector. Conversions are surprisingly fast compared to other sites. I am using to convert many years of t-shirt, hat designs and logos that were created raster. Since you cannot even download a single sample, you have to rely on their description of their service and the quality. You are kind of risking your first month payment of just under $10.00.
For me it is worth it though I have to say I hate how they throttle the conversion. According to their own site:
"High Performance: Nobody likes to wait. We respect your time, so we make sure we are fully utilizing state of the art GPUs for deep learning, and run carefully tuned and massively parallel classical algorithms on multi-core CPUs to bring you the best vectors in the industry ASAP."
They do not respect your time as much as you may think. I do not want to go to a site to convert and image and then have to go back or wait to do another. I want to get them done so I can do other work. Their system though frequently complains that I am going to fast. That is kinda crazy when I am only converting one at a time, saving and then loading up another image. I am essentially going at the pace of their software/capability. I have even spread out the time to avoid this message and sometimes still encounter it.
I did recently check out a redit thread that gives me a clear idea that this is not abnormal. Seems just about all of the posts I read gave quality good reviews and throttling bad reviews.