Depends on how "occasional" you plan to use it in the car.
From the other thread, you see the image I posted of the H8 clipped to an old WeatherTech Cup Phone holder. While it's not too much of a pain to put in and out of the car, it is nice to have two identical units, one for home and one for the car. They are programmed 80% identical as there are repeaters I hit in the car that I'll never hit at home.
Having one unit to do both isn't the end of the world, but for the price point, I bought two just for that reason.