What distinguishes xantax from ativan (lorazepam)?

Xanax (alprazolam): Both are benzos sedatives/anxiolytics. Ativan is shorter-acting than xanax (alprazolam).

Onset, duration: Both are benzodiazepine receptor agonists and are strong anti-anxiety medications with abuse potential and a host of side effects including sedation/dangerous while driving. They can have a dangerous withdrawal if not appropriately tapered. Xanax has faster onset and is more quickly metabolized. See: http://emedicine.medscape.com/article/2172250-overview

Benzodizapines: Both are benzodiazapines with addictive potential. The regular release form of Xanax has developed some notoriety due to deaths associated with withdrawal.