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.
There are literal points that should be noted, when you choose Bitcoin as a currency to save in, what are you saving towards?
Don't save in Bitcoin when you offer to purchase something with what was saved in Bitcoin, volatility can be a hindrance at the exact moment when the funds is needed.
Savings can be done in Bitcoin when there is nothing at the moment of buying, some may regard it as store of value instead of savings.