The initial question has transformed to
a point I have never claimed for.
I think we should go on using 'calories' because,
as many of you said, that's what students are
familiar with in their daily life. I'm sure
that only a non-significant part of them have never
heard about 'Coca-cola light', if any.
Indeed, for me a better reason is that 'calorie' covers perfectly
the need to refer to 'the energy needed to raise
the temp. of 1g ...'.
That is, there is a physical reason to introduce
that unit.
However, a different question is the need for using
'Calories'. At least that's the impression I've gotten
from your contributions.
I doubt about its usefulness for students after the
first or second year.
But, of course, it is trivial !!
On the other hand, droping 'Calories' in favor of
the 'k' prefix, won't mean to do the same with
units like year, day, lightyear or the like. It's
completely another story, because these last terms
uniquely suite some very common orders of magnitude.
This doesn't happens with 'Calorie'.