Thanks for the reply.

All my conclusions about what could be the plus and minus of various systems, were based on two things:
A. The reviews and complains I have found in youtube and other sources.
B. My view as an engineer, from the materials used and the Scientific laws that apply on the solutions I saw.
So for a moment I will "forget" what reviewers are saying
(I accept that many people do not have deep knowledge and their opinion can be wrong),
and I will stick on science.

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Bigger mass needs bigger force to accelerate at a required level.
And it is obvious that a printing bed with the required frame to support it,
is heavier than a hot end and the required bar to support X movement.
And we must not forget that during printing the bed is becoming heavier, as the printed object is being build up.

And since my requirements ask for a bed that is in "big" side of 3D printers that cost less than $1K
(and in this price I include any modifications needed),
the bed weight is increasing by square, and that of printed object by cube.
while hot end weight remains the same and only the X bar weight increases linearly.

For example moving to a 400X400X400 printer from a 200X200X200, means that bed weight is multiplied by 4.
And (maximum) printed object weight by 8.
(While X bar will have just double weight, and hot end is the same.)
That requires about 6 to 7 times bigger force to move the bed and the object.
So how this solution can be faster than those bed is not moving at all, or is moving a little vertically on layer change?
How those bigger forces will not create bigger vibrations?

I suppose that most of users print at low speeds (40~60mm/s) because printer manufacturers advice so.
And that's because cheaper printers have less rigidity.

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Purge walls are needed also for the many in to one out solutions.
Actually they need more waste than side by side dual heads.
Because multi filament heads on every change they mix a little the two filaments,
so a bigger quantity must be wasted.
Specially if one filament is a water soluble one ...

I will consider again dual head, because I found that there are dual heads in one body.
So probably the can be aligned with less effort.

INDEX is not an option for me, since I do not need most of what they can do,
and I do not see any such options within my budget.

Also I do not see any Delta option in the size I need.
Delta solutions are small if your prints have cylindrical shape.
If not, they are huge compared to XY printers.

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I still do not understand why you ... throw in garbage bin Creality printers.
Do you have any specific objections on why they should be selected?
Looking in many details the construction of Creality and Tronxy models,
I found that Creality has better quality both on the parts they use,
as also that of construction solutions.
Do I miss something?