BTC can't be better or worse than cash, it is just a different thing, BTC is like stocks, you can invest cash in it, but you still can't buy grocery for BTC
Bitcoins and money are practically same yet sometimes the bitcoins is superior to anything the money and those cases are the bitcoins has high security nobody could hurt bitcoins however money could be effortlessly hurt the costs of bitcoins are going high and high yet the costs of money don't change that is the reason bitcoins is superior to money.
The way I see it both has their own worlds and function to its users. Cash being in the physical world only means we use it in a daily basis like buying foods or for transportation etc. While bitcoin is in the digital world which means it is technologically more advance than cash, it has more uses and has more advantages that is why it is much better than cash.
Soon in the future, when technology already become more advanced by the time, cash and bitcoin will trying to compete even harder. maybe right now, as you said both have their own worlds
but it's not for long, the adoption of bitcoin will increase alongside with the growing of technology advancement, the phyiscal cash will become obsolete and any government will try to digitalize all their currencies.