I think all the arguing on both sides here is pretty stupid.
There's nothing intrinsic about points that requires users to buy a certain amount in advance. That was a design decision made by MS and Nintendo. You could offer a points system along with a "buy just enough to cover the game" option.
Likewise, there's nothing intrinsic about cash systems that make it impossible for cash cards to go on sale. Individual jurisdictions have different rules about gift cards, cash equivalents, tax rules, etc but there's nothing inherent in using a cash system that prevents sales.
In terms of the complaint that 800 MS Points is $10.00 while 800 Nintendo points is $8.00, again, that's just an implementation detail. There's no reason points systems have to be 1:1 with cash and there's no reason why they can't be 1:1 with cash.
It's all about how it gets implemented. In practice, MS points cards go on sale frequently and there are a number of giveaways online. In practice, most point systems require minimum purchase requirements. In practice, few cash systems do, although PSN's sort of does, and sort of doesn't, depending on your use case. In practice, retail availability is not connected to cash versus scrip but rather connected to the company's efforts to get things in stores.
So I don't really understand the disappointment or excitement here. Let's wait and see if Nintendo screws it up or makes it work.