While there are many different types of nail files, somewhere there is the perfect one for you. The decision lies in the types of nails you would like to file. If you have natural nails, you would need a different file than those who have acrylic nails. How often you are planning to use it? If you are a professional and plan to use it for your business, you would need a nail file that can hold up to that type of constant use. On the other hand, if you are just looking for personal use, there are plenty that would last you awhile.
Determine how often you intend to use the electric file. Will you use it all day, everyday? Will you use it just at home? Will you only use it once or twice a week? The durability of the nail file will have a direct impact on the price.
If you do intend to use the file every day, do you need a cordless file? The newest electric nail files run about two hours on a single charge. If you will be using it more often, maybe your best bet would be to stick with the corded versions. That decision alone can drop the price considerably.
Deciding on the bits for your nail file will also help determine which file to choose. Carbide bits are easy to use, and generate the least amount of heat while diamond bits can be used for more than just nails. Some of the diamond bits can be used to drill the nail to put on a charm.
The noise and vibration each file makes is individualized to each electric nail file, and depending on how much you are planning to hear and hold it, it will be an important feature. Consider a file that won't vibrate your hand off or even bruise your bones.