I think your first criterion is how the anesthetic would be applied: inhalation or injection.
You are right, in the movies the criminal soaks a rag in some chloroform and presses it to the victim's nose and in 0.5s the victim is unconscious. But it doesn't really work like that, even if the victim was breathing deeply, which probably they wouldn't be. Many inhaled anesthetics in use these days are still halogenated hydrocarbons like isofluorane.
Forcibly making someone unconscious with an anaesthetic in perpetration of a crime would be difficult, risky business. All anesthetics will kill someone if the dosage is wrong, and the correct dosage is at the least a function of body weight. The criminal would have to be able to do some quick math on the fly to calculate and administer the correct dosage. Maybe the criminal is an anesthesiologist?
Another factor that would have to be considered is the length of action. In surgery, multiple anesthetics are often used - for instance, one quick acting drug to start anesthesia, and another longer acting one to maintain it.