Many hosts have really crappy malware scanning, some have very good ones. It just depends. In many instances they leverage third-party providers and pass the scanning off the end-user.
Also understand that there are different types of scanning. Most hosts, if not all, are mostly interested in server level scans, not application scans and those that do application scans do a very bad job.
Take care
In the interest of full disclosure I run a scanning service so you might just ignore my feedback as nonsense. I also happen to partner and work with hosts a lot, which is where my feedback comes from. Do with it as you will.