A compact vaporizer is a chain: battery heats the coil, coil vaporizes the liquid in the chamber, and the vapor travels through the airway to your mouth. If any link is weak, the whole experience suffers. For example, a small battery might not deliver consistent power, so the coil heats unevenly, leading to burnt hits. Or a tiny chamber means the coil is closer to the mouthpiece, so you risk pulling hot liquid into your mouth if you draw too hard.