Bitcoin is one of the most talked about topics of the 21st century and for good reason.
It really isn't. If it were we would have had reached mass adoption already!
This means that all Bitcoin transactions are recorded on a public ledger, so no one can manipulate or alter the data.
The fact that it can't be altered isn't because bitcoin uses a public ledger, it is because of Proof of Work that costs so much money to attack that it becomes impossible to alter the ledger in practice.
In comparison almost all other altcoins have public ledgers too but many of them are pretty easy to alter later on. For example ETH doesn't have an immutable blockchain since it is centralized and they can easily change the blockchain as they did once before when they lost money in DAO and reversed all the blocks.
It also means that all Bitcoin transactions are instantaneous, with no third party or middleman involved. This makes it much faster and more efficient than traditional methods of payment.
Let's clarify something here, when we talk about speed of transferring money we refer to two things:
1. The time it takes the money to reach its destination
2. The time it takes for the transfer to become irreversible.
When you say instantiations you are referring to #1 which is obviously reversible but since the time it takes for bitcoin transactions to become irreversible is the time it takes to confirm a tx and that is on average 10 minutes you are right that bitcoin is still the fastest payment method.