So my normal train started from New Beckenham instead of Hayes this morning. I chose to rush breakfast and dash out the house to make the cannon street train before it, but to change at New Beckenham onto my normal train. The result is a lovely very empty train. I know from past experience that once the longer tube trip and extra stopping of the Cannon Street train is taken into account both get me to work at almost identical times.
I think when it is an option I will always start with an empty train.