What is better for Japan winter travel: eSIM or pocket Wi‑Fi?

For most travelers, an eSIM is more convenient than pocket Wi‑Fi in winter. An eSIM doesn’t require you to pick up or return a device, works as soon as your phone connects to a local network, and avoids the extra battery that drains faster in cold weather. Pocket Wi‑Fi can be useful for groups, but you have to keep it charged, dry, and with you at all times. If the router battery dies in the middle of a snowy day, everyone loses connection. With an eSIM, your phone connects directly to the network, and you can keep it warm in an inner pocket to preserve battery life.