[Chemical generators vs oxygen tanks]
There are advantages and disadvantages to both.
The Passenger Service Units (PSU's) are a complete
module that are easily reconfigured with the
airplane, but plumbed oxygen
requires more hassle, obviously.
Some folks don't like the plumbing all over the
plane with pressurized oxygen, but it is lighter than
all the generators, which are a bit hefty.

Interesting. I would've suspected that pressurized oxygen would be
heavier.

In any event, when I'm on an airplane I'm nervous enough that it's a
hurtling kerosene tank. Pressurized oxygen and plumbing, or chemical
oxygen generators, give me the heebie-jeebies. I would've thought that
the pressurized oxygen was heavier due to tankage but maybe the O2
cylinders I see in hospitals/shops are way overdesigned compared to
aircraft weight standards.

Now, smoking while on a hurtling kerosene tank that also has chemical
oxygen generators and/or pressurized O2, that does not strike me as the
right thing to do at all! It's not that I'm afraid of flying, it's
just all those risk factors being put in the same place. In the shops
I work (related to public transportation but generally not exposed to
the public) having any two of those four things in the same place
would have you shut down so quick by the safety people, and we aren't
even hurtling through the air!

Tim.