This is a conversation that comes up a lot, and as I’m adding a ETH 2.0 rollups to the comparisons section part in the wiki, I think it’s a good convo to bring to the forums.
I’ve gotten some good insight into how a Parachains compare to rollups from Rob H:
Architecture: Parachains are most similar in implementation to an Optimistic rollup and most similar in architecture to a ZK-rollup, because we actually run a validity proof. In our case, the proof (the approvals protocol) is interactive, unlike ZK-rollups which are non-interactive.
Unlike ZK-rollups, there are no difficulties in creating parachains with turing-complete logic. (this is a fundamental weakness of ZK rollups, because turing completeness within ZK circuits is not easy)
Optimistic rollups are required by architecture to have their ‘sequencer selection’ logic live in their host contract. This is because the contract needs to accept blocks which may be bad, and may not be executed, and needs to filter out spam. Parachains, like ZK rollups, can encapsulate the sequencer-selection logic within their validation code.
And will leave this here for any other insights from those that might have good thoughts around how to best articulate this comparison.