It's well established that shorter block times result in less security per block, but it's also possible shorter block times result in less security per unit of

It's well established that shorter block times result in less security per block, but it's also possible shorter block times result in less security per unit of time (given equal total network hashing power) This is due to the time it takes for newly mined blocks to propagate through the network. Miners work on old blocks a larger portion of time, leading to more forks and waste of mining resources. Of course Bitcoin has far more hashing power than Litecoin or Dogecoin anyway, since the hashing power will correlate with the value of the mining rewards. IMHO the real solution for both transaction speed and scalability is networks of "off-chain" transactions processors that occasionally "settle" on the blockchain. Of course such networks should retain the open and trustless properties of Bitcoin.