Although more research is needed into medical marijuana it does have the benefit that it improves mood and makes a person feel better. Painkillers take away the pain but can have unpleasant side effects and does nothing for a person's mood. Medical marijuana might not have as many side effects as painkillers.
It is very sad how many older people especially get addicting to painkillers, and now it has become a problem with younger users as well. There is no research that says that medical marijuana is addictive, other than that people will use it continuously to deal with their pain, but without the deadly side effects of pill addictions.
Painkillers are addictive and can have a slew of negative side effects. Medical marijuana does not have these drawbacks and is therefore more beneficial than painkillers in this way. In small enough doses, marijuana also does not cause the complete fog that a painkiller can and can allow a person to function as normal.
No, there are no additional benefits to the use of marijuana over painkillers. The use of medicinal marijuana can help to alleviate pain, but it does not do anything else for the person taking the marijuana. It is more logical to believe that clinical strength painkillers can contain more beneficial medications than to believe that marijuana does.