What is the difference between portable and mains nail drills?

There are portable nail drills available on the market that are powered by an inbuilt battery. For all their lightness and mobility, portable nail drills cannot produce power comparable to mains-powered nail drills. Compared to Korean mains-powered nail drills, the torque of the battery-powered counterparts is noticeably lower.

Portable nail drills have no protection against overload and overheating, so they cannot be considered reliable enough.

On average, portable nail drills are more expensive than network nail drills. For the autonomy of the nail drill you will have to pay extra $100-150.

For most masters, a Korean Strong or Marathon nail drill is the best option, because at a lower cost (than portable nail drills), they are more powerful and reliable. Thanks to the "110/220 V" switch, the Korean nail drill can be used anywhere in the world. 

Unless you are working on customer visits, there is no point in buying a portable (cordless) nail drill.