Multiple temperature settings:
Regardless of which vaporizer you purchase, it should have multiple temperature settings. The medicinal properties in the cannabis are activated through the process of heating and so you must have control over the temperature setting. The key is to heat the cannabis as much as possible without burning.
Your vaporizer should have temperature settings for 200°C or higher.
Portability/Discreetness:
You may be administering the medical cannabis multiple times throughout the day (on average 3 times a day) in order to achieve continuous pain relief. Therefore, at times when you are out in public and need to vaporize, it may be easier to medicate if the device is easy to carry, light, and discreet.