Despite what some might think, bigger isn’t always better. We talk about the right size furnace or air conditioner for our homes, it makes sense that a dehumidifier should be sized right too.
First of all, I suggest you take care of everything you can to reduce moisture in the first place. (Home as microbiology experiment? Moisture, keep it reasonable and stay safe) This is a lot like what I suggest in terms of heating and cooling in a home. Air seal and insulate first to make the home more efficient, then change the HVAC system. The same principle applies to choosing a dehumidifier: reduce the need first, and this will allow for a smaller unit. It might be smaller, but it will use less energy.
Since basements and other spaces sometimes need some dehumidification, consider the following chart:
ENERGY STAR® qualified models are better since they use less energy, and you can check the EnergyGuide sticker to see what yearly energy consumption a model has.