It's a good idea to save in bitcoin but then bitcoin is volatile in short term so the risk is quiet high in short term but if considering long term then bitcoin is best choice Viz vice with fiat fiat is best option for short term because it's leads volatile in short term so saving in fiat for just a little amount of time is good.
In my opinion, fiat is not recommended for both short and long term. You know how bad the fiat system is, which makes the value of our money continue to decrease due to inflation. So for those who understand this, they will not use fiat as savings even though for the short term, fiat is only good for transactions, otherwise not. If in the future every country has adopted crypto as a means of payment, maybe many will switch to crypto rather than fiat. Unfortunately, currently it only applies to fiat to be able to make transactions in each country. So whatever it is, saving in fiat is not a wise choice, even if you want to save for the short term, gold is the right choice, and for the long term in bitcoin.