If UTC was the primary trade pair on exchanges, how much faster would it be to transfer funds from one exchange to the next?
I've done some testing on this, the average for all exchanges is between 6 and 7 minutes. The slowdown is because they have a daemon that runs on a cycle, usually 5 minutes, that looks for and processes withdrawals and deposits. We have been considering ways to get exchanges to prioritize UTC transfers, may be able to get that if we bring volume.
And the difference between coins is only noticeable for those those with slow confirmation times.