For visual use on deep sky objects, all other things being equal, IMO
the 10" Newtonians would be better than the 127mm Mak-cass.

1) The 10s collect more light and concentrate more light into the
image of any given deep sky object. Small, faint DSOs would appear
brighter with the 10s. More stars would be visible in star clusters.

2) The 10s have shorter focal lengths. This translates into the
possibility of achieving wider true fields of view with the 10s. As a
result the 10s would be superior to the 127 for viewing large DSOs.
(The option of using 2" O.D. eyepieces will also be beneficial.)

3) Assuming reasonably well-designed and well-built mounts, it would
be possible to beneficially use higher magnifications with the 10s.
This would make visible smaller and fainter DSOs. This will also
reveal greater detail in DSOs.

The 127 also has some advantages: It's a more compact telescope.
Motorized tracking is convenient. Some observers enjoy the challenge
of undertaking deep sky work with smaller apertures. Eyepiece
location wouldn't change as much. The 127 would be easier to
configure for non-visual use.

The longer focal length of the 127 would not be a disadvantage for
small DSOs or for using high magnifications.

Still, if the bottom line is the view in the eyepiece the 10s hold a
very definite advantage for large as well as small deep sky objects,
for fuzzy DSOs as well as for open and globular star clusters.

If compact size is critically important, if a person simply enjoys the
challenges associated with using a smaller telescope, if there's a
willingness to sacrifice large fields of view, or if motorized
tracking is very important for someone then the 127 Mak-cass. *can* be
effectively used for quite a bit of deep sky work. Just don't expect
the eyepiece view with the smaller Mak-cass. to equal or surpass that
of a 10 inch Newtonian. The 10 inch will show *all* deep sky objects
better.

Sketcher
To sketch is to see.