What is the difference between barbiturates v benzodiazepines?

Both are. Sedative hypnotic's and both enhance the activity of inhibitory neurotransmitters in the cns. Both exert action at the gaba receptor complex. Barbiturates also block excitatory neurotransmitter. While the chemical structures are different, the most significant differences are the wider therapeutic window, lower drug tolerance and lower propensity for abuse with the benzodiazepines.