best pocket wifi for 3 week trip?

Please don't tell me to search on 'pocket wifi' as I've just done that and read several pages of search results and didn't find the answer. :) We'll be flying into Narita and would like to pick it up there if possible, arriving on a Sunday afternoon this summer. Are there several companies to choose from? All about the same or is one somehow better? We'll use it mostly when we're out and about, or if our accommodation's wifi isn't great. Thanks!