If you're choosing a budget SIM with a 20GB plan, the balance between speed and cost is really important. Recently, I've tried various options, but ultimately, the best choice depends on how you use it.

First, if you're prioritizing speed and looking for a 20GB budget SIM, povo is seriously highly recommended. Since it uses the au network directly, the stability is completely different. The basic fee is 0 yen, and you purchase data as needed, making it perfect for people whose usage varies month to month. Also, the effective cost when using 20GB per month stays in the low 2,000 yen range, which is attractive.

Ahamo offers stability comparable to the Docomo network, but it's better for those who want to pay the same amount every month. With a 30GB plan costing less than 3,000 yen per month and free overseas roaming, it's convenient for business travelers. However, since there's no plan exactly matching 20GB, you might end up with a bit more capacity than needed.

If cost is the top priority, Japan Communications SIM at 1,390 yen is hard to overlook. It's among the cheapest 20GB budget SIMs. But keep in mind, since it's an MVNO, speeds during the daytime might slow down.

In the end, if you need speed, go with povo; if you prefer a fixed monthly fee, ahamo; and if you're all about saving money, choose a SIM based on your own priorities.