A portable coffee grinder solves a different problem from a countertop one. What matters is grinding without an outlet, in a bag, on someone else's counter — not the last few microns of particle distribution.
An electric portable runs on its own battery and does the work for you, at the cost of a charge to manage and more that can go wrong.
A hand grinder never needs power and is usually more consistent for the money, but you turn the handle — a minute or two per cup, longer at espresso fineness.
Neither is better. The question is whether you would rather carry a charger or turn a crank.
Capacity per grind. Most portables hold enough for one or two cups. For three or more you will be refilling.
Charging. USB-C from a power bank, a laptop or a car is what makes it genuinely portable. Check what the charger actually accepts.
Cleaning on the road. Something you can empty and brush out without tools.
Grind range. Many portables are clear about filter and vague about espresso. Where no espresso range is published, assume there is not one.
Probably not.
Portables are built around a small burr set and a small chamber. That is exactly right in a hotel room and exactly wrong for a household brewing a litre of filter every morning.
If it will live on your counter and never leave, buy a plugged-in grinder instead — you get more burr for the money. Part of what you pay for in a portable is the fact that it travels.
