Airflow
I have one of those meters, but their readings are not always completely consistent
When i had a Rainbow D4 SE it wouldn't register on the meter
My Rainbow E2 (black) as you can see in the picture pulls about a 2 i have seen it register in at about a 2.5 as well.
As for miele pulling a 9.5 maybe at the vacuum body itself but at the hose end the most i have ever seen a miele pull at the hose is a 5.5 both my older Silver moon and a newer S8 (forgot the exact model) can pull a 5.5
Is Rainbow the overall best? In my opinion no their airflow is mediocre compared to other door to door canister, and they are a lot of work to maintain i would much rather use a bagged system, i think the most powerful canister I've used is the Lindhaus Aria (reads in at 7.5 max) but i would not recommend one to most people as they are not as user friendly as some other machines.
In terms of performance and convenience I'd take a Miele over a rainbow, but the rainbow is much more versatile, being able to pick up water, shampoo carpets (with the right attachments, etc.
The newest model Rainbow should clean better i've never directly compared the two and no longer can as i parted with my D series models in favor of the E2
I think you should switch the powerhead for a bare floor tool when doing your hard surfaces.
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