On Jan 4, 8:08 am, wrote:
Running off is much easier on the boat and the crew than riding to a
sea anchor or even heaving to. ...

I dunno about that, most times it has seemed to me that heaving-to
provides the smoothest motion...

Some boats are going to roll and slew about when running off. That
should be controllable to some extent by over-trimming the storm jib
and heading up onto a broad reach, but YMMV. At some point, though,
heaving to will not be a viable option and running off is going to be
less stressful than anchoring. On boats that don't roll so much
running off will likely be more comfortable than heaving to right from
the git go as long as you keep enough sail up and trimmed.

... the series drogue is mostly hanging down. As the boat picks
up speed, more of them stream and drag increases. Boat speed
increases, but not as sharply.

Yes, but generally the series drogue is sized to be very draggy
compared to other drogues and it doesn't have the swift transition
from modest drag to high drag that the variable drag drogues have.

... What do you think of the task of switching from one to other if the
sea state gets bad enough to warrant? ...

I do not think it is practical to switch in genuinely dangerous
weather.

And which would you deploy
first, which would be the "ultimate"?...

It depends. It is no big deal to set or retrieve the drogue and if
conditions were right and I was headed downwind anyway I wouldn't
hesitate to set it. The sea anchor is pretty much a "hail Mary" for
me for use when there is no other escape (eg. on the dangerous side of
a storm or lee shore when beating becomes impossible). I think the
sea anchor will keep you from capsizing in worse conditions than the
drogue but that may be cold comfort if the superstructure has been
swept away and you are sinking...

-- Tom.