Ethereum

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Ethereum Protocol

Ethereum blockchain platform views smart contract as a first-class element and includes a virtual machine for executing smart contracts.

Ethereum is configured to have around 13-15s interval between blocks on average. This value is that much longer than the time required to propagate information throughout the global blockchain network.

Because of the shorter block time, it is much more likely in Ethereum that multiple new blocks are created concurrently at the a similar time.

Ethereum addresses this problem with a modified GHOST (Greedy Heaviest Observed Subtree) protocol.

I don't understand this point. I will need to refer to the yellow paper of Ethereum to understand.

Processing

The processing of each transaction is fairly similar to Bitcoin. Transactions appearing in a block might be discarded when the block is overwritten due to chain forking.

Participants of Ethereum cannot be sure whether all miners has dropped and discarded a transaction, unless a transaction superseding it (i.e., having higher nonce) arrives.

Due to the higher block rate, Ethereum has to wait for 11 confirmation blocks to declare a transaction as committed.