Monero still the best privacy coin in the world hands down
Nothing else compares to Monero's feature set, and security. I think mimblewimble would be considered the most fungable now but that tech is years away from real world use.
I dont understand why. If it is stripped Monero with less opaque ledger how could be more fungible? Grim should be less fungible but more scalable. But you are right that only future can answer that. Monero managed to reduce transactions sizes so far and have more in plans. We have no ideas what future will bring.
BTW I found this on twitter: https://twitter.com/Trezor/status/1125429283697172482
From what I understand of mimblewimble is there are no records kept which yes will make for great fungability but how can you prove you made a transaction in the past?
Everything in life is a tradeoff and you need to choose by what balance you are willing to accept. If you want a fully transparent ledger then BTC is top dog for the job.