Roff summed it up nicely, but it's worth remembering that even if your watch turns out to be running outside of COSC specs when you buy it, the watch will be under warranty (if you buy new from an AD), so you can simply get in regulated free of charge. None of the movements that Breitling use have any problems adhering to COSC specs when adjusted/regulated properly, so you should have no problems at all.
Its worth remembering that it is the movement that is Chronometer tested, NOT the whole watch. Occasionally the deviations outside of COSC specs that people see on new watches is as a result of the casing up process. But as I say, a regulation is a very simple fix and won't cost you anything is you buy new.
That said, COSC specs are still -4/+6 seconds a day, so if that level of accuracy is not sufficient for you then you should probably consider quartz. However I'd suggest that for 99.9% of the population, running your life to a zero tolerance of timekeeping is one OCD step too far!
