Portable car heaters offer several advantages. They are highly flexible and can be easily moved from one vehicle to another. They are also relatively inexpensive compared to built-in heaters and can be a quick solution for warming up the car on cold days. However, they may have limited heating power and may not be able to warm the entire car evenly. They often rely on battery power, which can drain the car's battery if used for an extended period.
Built-in car heaters, on the other hand, provide more consistent and powerful heating. They are integrated into the car's system and can warm the interior more effectively, distributing heat evenly throughout the cabin. They also don't rely on the car's battery as much, as they are usually powered by the engine. However, built-in heaters are more expensive to install and may not be an option for older cars without the necessary infrastructure. Once installed, they are not easily removable or transferable to other vehicles.