In my opinion, bitcoin is an asset. Why is that? Let's look at the bitcoin price when it first appears. Has not it gone up many times now? So making bitcoin as an asset is a very appropriate choice.
If you consider it an asset then you do not need to use bitcoin for everyday purposes, you tend to think about long-term prospects and the fact that bitcoin serves as a medium of exchange every day. It is more perfect if we think of it as a currency that has a double role as an investment asset.
Well it could be both but it really depends on the user on how he/she treats bitcoin. For example, if someone needs cash for paying obligations and he/she does not have fiat at the moment, he can always convert bitcoins and use it as a payment for EMERGENCY PURPOSES. On the asset side, one might see bitcoin as a future investment due to its high volatility. In a short matter of time, one can incur profit compared to bank investments that is too time consuming while at the same time low in profit. Bitcoin is very flexible when it comes to these matters and it really depends on the person on how he/she uses it.