I'll take the bait. I would use only absorption.
Why? Because I can control how much I use.
I would treat the front 1/3 of the room first to deal with first reflection issues. Then I would proceed with caution.
Having said that, I don't use specialized products. I use furniture and wall hangings and thick Persian rugs with heavy felt underlayment.
Has anyone listened to a room with the old concrete acoustic ceilings? They were the first gen version before the softer asbestos version came out it the late 60s and 70s. I had a house built in the late 50s and no room has sounded as good from a clarity and bass perspective.
My thinking is that bass goes right through and is reflected back with softer absorptive/diffuser materials but that the concrete material has a small but noticable effect on all frequencies.
Ceilings with this material cannot be scraped. The whole ceiling needs to be cut out...that's why they're still around. Flipping a house with this ceiling is not cheap.