CCA,
There's a number of advantages and disadvantages to be considered when comparing gaseous (bottled) oxygen to that available from chemical generators, here's a few of them -
(1) Oxygen available from a chemical generator is not subject to the risk of pressure loss / system rupture, as was the original point considered when you began this thread,
(2) Once started, a chemical generator cannot be turned OFF, whereas the gaseous supply can, leaving a 'mains' supply in reserve for any passengers requiring supplemental oxygen. (on some aircraft, supplemental oxygen is available full-time from the main gaseous supply, not possible with oxygen supplied from a chemical generator).
(3) Oxygen available from a chemical generator can not be supplied 'under pressure', thus it would have no flight deck use for the COMPLETE prevention of hypoxia if exposure to low pressure at high altitude was sustained or delayed,
(4) The duration of oxygen supply from chemical generators is quite short (10 to 15 minutes at the most), whereas the duration of supply of gaseous oxygen is limited only by the amount that the operator wishes to install and carry. This point is important, we operate 2 versions of the B777, one with, and one without gaseous 'bottled' oxygen. The much longer availability of oxygen from the gaseous system enables operations over regions of extended high terrain (e.g. Afghanistan) where the MEA is up to 18,000 feet, and passengers must remain on oxygen for some time after the initial emergency descent, until descent to 10,000 feet can be accomplished at a much later stage.
Your comments regarding the availability of PBE equipment to passengers is interesting. I EXPECT (but don't know for sure) that the in-built oxygen system would suffice to prevent hypoxia for the duration of an emergency descent, but what would kill such an idea is that the donning time, particularly for a passenger who has never used one before, would well exceed the Time of Useful Consciousness at high Altitude.
Whether PBE should be made available to passengers for use during smoke and fire emergencies is an entirely different issue. I can envisage that one day it may become a requirement to have PBE equipment available for all passengers, but not to cover the oxygen requirement for high altitude depressurisation and emergency descent.
Regards,
Old Smokey