The texture of rice can become quite gummy in a slow cooker. It is best to use the specific type of rice that the recipe specifies. If the recipe does not specify the type of rice to use, then your best choice is long grain converted rice. The texture of the rice will be retained best of all the types of rice on the market.
But don’t exchange this rice for a different type specified in a recipe, since that recipe would be designed for that rice! But whenever the recipe just states rice, you will get the best results with long grain converted rice.