How can I say it?
Everyone's phone and usage situations and circumstances are different, but it's mostly you.
For example, for myself, if it is just a daily trip for a day or two, the 10,000 MA is almost enough, and if it is a long time outside without charging time, it may need 20,000 MA!
The mobile phone is iPhone8, the charging treasure is: green link 10,000 ma Apple charging treasure, about enough to charge about four times, so it is not a problem to travel for a day or two, the charging treasure comes with mfi data cable, charging fast, the size is just convenient to carry, go out into the bag can be stuffed, will not feel burdensome.
There is another factor, if you are two people to use together, it is recommended that 20,000 ma, otherwise the phone capacity is not the same, may be 10,000 ma a person once or twice out of power.
20,000 Ma for me is more tired, the weight and size will be more obvious than 10,000 Ma, if not for a long time outside I generally do not bring 20,000 MA mobile power.