It most definitely differs between regions. You cannot use Nintendo eShop pre-paid cards to buy goods on the Wii Shop Channel here in North America. They are two completely separate store fronts with their own brand of currency.

It's a shame you can't buy prepaid wii points cards anymore AFAIK, since there's still a few things on the wii store I'd like to buy.

eshop credit is not the same as wii points, maybe you can find a card online. I bought eshop credit that way and they emailed me a code, I guess you can do the same thing with wii points, just find a legit store that sells them for the region your console is on.

The Wii U store uses Yen and the Wii Shopping Channel points here. Yet according to Nintendo's site you can register the card while using the Wii Shopping Channel and it will give you the equivalent points. Wonder why they don't do that for all regions.

For those can read Japanese: http://www.nintendo.co.jp/support/nintendo_eshop/payment/aboutcard.html

It's mentioned right at the bottom of the page.

I won't bother linking to it (it wasn't the main focus of the thread), but I did find a post on the Nintendo of America tech support forum where someone mentioned buying an eShop card and not being able to add it to the Wii Shop Channel. For whatever reason, those eShop cards are only good for the Wii U and 3DS eShop. To get more points for the Wii Shop Channel, you need a credit card.