"No" writes:
I'm sure if both were starting at same time that sucker would blow
pretty quick.

Breakers tend to be heat-based, so a short pulse of over-current is
usually acceptable. The purpose of breakers is to protect the wiring
up to the outlet, not to protect the device plugged into it, so they
try to simulate how much heat the wiring is generating and shut off
the current before the wire's insulation breaks down.

The only time I've seen a breaker blow "pretty quick" was when it was
completely shorted.