How long does it take to propagate a new broadcasted message in the Bitmessage?
Curently, with around 5000 nodes, a message shouldn't take longer than about 15 seconds to propagate. Typically, it's faster.


Messages are forwarded if the Proof of Work is sufficient. There is no signature verification on forwarding, since only the recipient of the message can verify that. Nowadays, PyBitmessage runs the decryption attempts in a separate thread, therefore forwarding and decryption run in parallel.
Some versions have different delays in forwarding depending on what type of object it is, some do not have delays. But this has nothing to do with decryption attempts, it is an attempt to mitigate timing attacks.
For propagation size does matter, because it takes longer to transfer, however I don't think the difference is that big, in particular if you're on a fast connection. For decryption, the data itself is encrypted with AES-256-CBC, and that's pretty fast, on my laptop I get like 100MB/s, so you shouldn't see a big difference.
Latency does influence the speed a bit, but some network operations are asynchronous, at least in PyBitmessage, so from practical point of view it's not a big deal.
I don't understand this. It takes a bit longer if there are more nodes in the network, but on the other hand if they are well connected, it's faster. PyBitmessage will by default attempt to maintain 8 outbound connections, and refuse incoming if it has more than 220 total connections.


Recently a new stats website was launched: https://beamstat.com/, which works nicely, just the node count is incomplete.