Marinol is a synthetic THC extract which does not contain other useful cannabinoids.
source "However, to those thousands of patients who find Marinol ineffective or less effective when compared to whole smoked marijuana therapy, this reclassification provides little relief."

"Marinol is not necessarily an adequate substitute for whole smoked marijuana because it lacks several of the drug's medically valuable compounds, known as cannabinoids. Therefore, this decision is not a silver bullet for patients or politicians. Federal law still must be changed to allow those unresponsive to synthetic THC the opportunity to use inhaled marijuana as a legal medical therapy."

Sativex on the other hand is an oromucosal spray derived from natural extracts of the cannabis indica plant, it contains both THC and Cannabidiol. It is a British-made drug but for some stupid reason it is not easily accessible, only in Canada where it is available on full prescription. there are probably trials of the drug going on in the US now, your best bet is getting on one of them. The company that make it are called G.W. Pharmaceutical this is their website GW Pharma Website

source successful results for cancer patients with sativex