Whether you need a heater or not largely depends on where your fermentation chamber is going to reside. If you want to brew ales in the winter where it truly gets cold and you keep your chamber in the garage, you may need the heat option to keep a stable 65-68F.
Most commonly, people primarily need the chilling option (chest freezer, mini fridge, etc) to cool the wort to pitching temperature before inoculation with yeast and to deal with the early fermentation process producing a considerable amount of heat.
If your chamber is going to reside in your garage and you live somewhere hot, you'll probably almost never need the heating component unless you want to get nuts with high temp saison fermentations.