|Here's the skinny:
The WonderMill replaced the WhisperMill, but is essentially the same. It's reliable, fast and a bit more quiet than the NutriMill. The WonderMill can yield about 10-12 cups of milled flour (8 cups of grain) in one milling; much more than that will overfill the flour canister. But because it's fast, milling two batches of flour are no big deal. The WonderMill has basically one coarseness setting. It has a knob you can turn to adjust the coarseness, but I have noticed very little difference. It produces a consistent, powdery flour that is great for breads, cookies, muffins, etc. You MUST turn the mill on before dumping your grain into the milling chamber. Otherwise, the mill will jam. Also, you cannot mill nuts, seeds, or anything oily. That is VERY bad for the mill and will gum it up.
The NutriMill has a larger capacity, and will yield up to 17 cups of flour (10-11 cups of grain) per milling. Its coarseness setting is more sensitive, and will give you a more variety in how coarse or fine your flour is. It is reliable, but it is louder and slower than the WonderMill. It is also more trouble to keep clean, as it is one unit with the removable flour canister on the bottom. With the NutriMill, you can dump in your grains, then turn it on. This is probably the most significant difference between it and the WonderMill. Just like the WonderMill, you cannot mill nuts, seeds, or anything oily.
Either mill is a great choice. Everyone has their favorite, and love whichever one they have. They are both good mills.