If I already have plenty of battery packs to use, is there any reason to get the 20W over the 14W. Is the only difference the number of extra batteries provided, or is there actually a difference in the panel itself?
EdgarBasically the 20W will do better in less sunlight because it has more surface area as Chao pointed out. And the 20W will do better charging 2 devices at once than the 14W. So if you see value in the trade off in weight and size for faster charging while using 2 ports and can do better in less sunlight then get the 20W. Otherwise 14W is perfectly 100% awesome and reliable.