If only Bitcoin is banned, I choose ethereum maybe.
but if Bitcoin is banned and all altcoin are banned. no choice.
If I'm not wrong first all other coins will be banned before they go for Bitcoin because bitcoin is the one more stable compared to other coins.
So once bitcoin is banned then for crypto investors no other options. But the good thing is bitcoin is a digital currency and it may not be banned in all countries at a time so you still get a chance to sell to someone else in this world and make money.