Why either or? I consider it both.
The fact that the value change (positevely) over the time is also the sign that this is a strong medium and not only a currency.
Almost all currencies change their value a lot, so this is not a point that disproves Bitcoin's status as a currency.
To me, an asset that is scarce and increases in value over time like bitcoin. Spending it is a waste, instead we should utilize its full potential to create greater benefits.
If you spend some, just buy more. That is an easy solution to what you wrote.