alt Hacker NewsUDP gives you practically no guarantees about anything. Forget exactly once processing, UDP doesn't even give you any kind of guarantees about delivery to begin with, whether delivery will happen at all, order of delivery, lack of duplicates, etc, nothing. These things are so far from comparable that this idea makes no sense even after trying real hard to steelman it.
UDP plus increment means that the client can request a snapshot to be re-sent. This mechanism is used in financial exchanges and works amazing.
This illustrates that the webdevs who write articles on "distributed system" don't really understand what is already out there. These are all solved problems.