Mass bench with ducting or half barrel bell?

Dear rocket scientists,
in October I’ll finally start building the first RMH for a friend.

@Thomas Rubino, your advice of just going ahead and starting was something I really needed (https://permies.com/t/186176/Rocket-Scientist#1739693) Thank you for that!

As it’s a first time I am trying to keep it relatively simple and on a budget where possible, without sacrificing quality too much.
It’s going to be a 6” J-tube with a 55 gal barrel. I’ll start another thread on the design and build soon. But I have some questions first, that I don’t want to crowd the thread with.

So here it goes:
The mass is going to be a bench the size of a single bed (90cm deep, 200cm long). I was planning metal ducting (150mm) with thermal cob and stones, following the Wiesner rmh "bible" .
Now I keep bumping into the half barrel bell benches and that made me think.
Could y’all help me with understanding the pros and cons of that system over the “traditional” ducting?
One difference I can see is that a half barrel bench has less mass, as there is a lot of air space (filled with the hot gases).
Is it quicker to heat up? More efficient because of stratification?
Can a half barrel bench be combined with the "juice box straw" design (the vertical exhaust goes into the bell and sucks the colder air from somewhere close to the bottom)?

I would also appreciate links to the best threads about the half barrel benches that you know of.

Thanks in advance

Edit: after watching Pauls Video about stratification chambers I swapped the word "bell" for "stratification chamber" to be precise, as Paul describes in his post (permies.com/t/74116/stratification-chamber-rocket-mass-heater#615962
Here's the video:

I hope you have plenty of spare reading time….. https://permies.com/t/122458/Advice-RMH-build-Hokkaido-Japan

Hey Fox, thanks for the quick answer. I have read (most) of that thread in the past. Will skim it for the bell and stratification chamber parts.

Hey Fox. That was a good read. Maybe I missed it, but there’s not so much discussion about the pros and cons of a stratification chamber vs traditional bench with ducting. Also most links in the thread go to very specific stratification chamber builds with columns for mass etc.
what exactly did you want to point me to?

Ah ok, I have not read that thread for a few years  myself but, I was pointing you towards the use of half barrels and I though there was some discussion about the benefits of stratification chamber over  a piped system.
Bell designs have become the more popular choice (at least from what we can gather from this forum and other written sources) because they offer a more free flowing system that is easier to start up and often easier to construct.
However if you want to use the encased pipe design it can still work fine.
The issues come from tight restrictions or too many bends or too long a stretch of pipe.
If you just use one straight length of clean, smooth bore pipe, then no problem, if you add elbows, bends or use small bore of corrugated pipe then the stove can be difficult to start up and get going.
A hollow bench offers no such restrictions and is a more modern approach.
There will be far more in depth discussions about the pros and cons, perhaps somebody else with more experience of such things can help?