I'd say a deflationary currency incentivizes less spending, not no spending at all. That's the difference.

Now, your point about Bitcoins only being good for storing money, but not for spending. I don't really understand it. Bitcoin is in no way inferior to fiat currencies if you judge it by its properties. In fact, you can spend it much easier and faster than fiat. The adoption problem is a separate problem and it has to do with government regulations to a large extent and people not understanding the technology to a lesser extent. Both problems are temporary. But let's say Bitcoin is accepted everywhere, since we are talking about the idea of a deflationary currency vs an inflationary one. What would be the incentive for me to own any USD?