What do you think will be the best and why?
The best will come from programmable privacy. Look at some projects that are being developed: Blacknet, Aleo, DarkFi.
Zcash uses zk-SNARKs, which are very good, but they need a trusted setup, which is risky.
Modern zk-SNARKs, like their Halo2, don't rely on the trusted setup.