Monero without a doubt, for the privacy aspect, and automatic block size adjustment as features that are already better than bitcoin.
There is so much development going on in the Monero sphere that I don't think any other alt comes close.
It's the only other crypto that I own right now. I don't have to wait for the end of the world in bitcoin to invest/hedge in another crypto.
Surprised it took so long to see Monero mentioned. If something "bad" happens to bitcoin it will likely be due to government taking advantage of the transparent and non-fungible nature of bitcoin to attack or co-opt it. In this scenario, Monero is the obvious choice as it would be resilient against such attacks.