Semi-debatable. Someone needs to set up a scientific
experiment here
It can breathe well enough on the floor. The floor area tends
to be colder too. Heat rises.
If the machine is on the desk, it may be subject to more vibration
(or less
).
Maybe that's something you need to worry about too.
And then, of course, it'll suck in bits of dust falling off your arms,
and germs you exhale (which will multiply inside the enclosure
and eventually eat away at the insides). Not to mention stray ants
attracted to sugary substances dropped on the desk when eating,
etc etc. Because, let's not forget it, desks also accumulate things
and dust and stuff and things.
Solution: balance the machine on a pin.
That desk position is further from the core of the earth, so the
machine will move faster through space, possibly colliding with
ever so slightly more cosmic rays. And it'll be closer to the
nefarious gravitational influence of the moon.
And if your house/office is hit by an earthquake, is it safer on the
desk or the ground? And is that the time when you regret having
decided to balance the machine on a pin?