Barry N. Turner wrote : in (clip) I don't even know if I could turn from a
sitting position. It would be terribly awkward for me (clip)
^^^^^^^^^^^^
A couple of years ago someone brought this up because of a physical
impairment. He even started a website aimed at helping handicapped people
adapt to turning. I believe one of the suggestions was to tilt the lathe
toward the turner, in order to duplicate the normal relationship a turner
has to the work. Tilting the lathe toward the turner is a lot like leaning
over the work.

All of this suggests to me that if you have your choice, it is easier and
better to stand up.