I have tried the drills that have batteries in the body of the drill [SEP] And while they don't seem to be bad, they just don't have the power that this one does.  I'm thinking it has to do with the size/strength of the battery in the drill's attached power supply.  While I do use this for my fingernails, I am using it more for my toenails and feet.  Toenails are thick and tough and I have trouble cutting them well even with good toenail clippers so being able to file them a little at a time is much easier.  Also, I have some very hard, thick skin on my feet and "grinding" that skin down is much easier that using a foot file.  This is a wonderful nail drill that's not just for nails - sturdy like a workhorse, it will make short work of messy nails or hard, callused skin.