Dirty Shoes and I recently got a new mobile line. Having used docomo some 4 years now and Softbank prior to that, this is my first time drifting away from the big 3 players, docomo, au, and Softbank (hereafter daS), and I would like to recommend getting a line not directly from any of the daS if you need to get one.
We got a Y!Mobile line, for one simple reason that it is cheaper than any of the equivalent plans of daS (and also because Dirty Shoes was bent on getting the Huawei P20 offered by Y! instead of its lower rung brother P20 Lite). The plans are as cheap as half the price what daS offers.
Before I deep dive further into what I call, the X-Mobile lines (because they are usually called something-Mobile), I’d like to raise the unfathomable fact that telecommunications companies do not appear to place value in loyalty. The benefits and discounts one gets from changing telecom companies is much much greater than staying with one. This is why some people I know change phone lines once every 2 years when their contract is up. Also, unlike in Singapore, where you can continue using a phone line after a contract runs out, Japanese companies give you a 2-month window to terminate your line with them after 2 years. If you do not do anything about it, your contract is automatically renewed for another 2 years and terminating during any time after the automatic renewal would cost you termination fees. This gives people more incentive to make sure they do not remain loyal to any phone company.
My visa has less than 2 years remaining—same for Dirty Shoes—so, many companies also do not allow us to sign new contracts with them. My other option would be to stay with docomo, but it’s just too expensive now that I have more commitments that came my way. That means, switching would be a better bet.
Apart from daS, there are tons of other mobile lines such as UQ, Y!, Line, mineo, OCN, Bic, Aeon, Rakuten and so on. But our options were just between UQ and Y! Mobile. The reason is because Y! is by Softbank and UQ is by au, while most of the other lines are independent companies borrowing part of the network from docomo. This means, when the network gets busy during peak hours, these many companies borrowing the network will more likely face speed issues as opposed to Y! and UQ.
With that, I think you see more reason why you should not go with daS. And if speed is of no concern to you, there are cheaper plans under the companies that borrow the network from docomo. In any case, not using daS can save you more money. But if you’re bent on using the major players, experience tells me that au has the best network coverage, followed by docomo and then Softbank.