>> Presumably, it's related to the handling of the environment variables?
> ($PROMPT present) and non-interactive ($PROMPT not present) use.
> which environment variables will be valid in which situation.
> (+ls, default behaviour). See also loginShell X resource.
> To compare the environment variables set: ``env | sort -o file1´´.
> environment (in a long unsorted list like ``"TERM=dumb"
> consuming. Another, sometimes faster option, is to use a "trace"
> facility to watch a programme (or two: GNU and emacsclient) working.
> streams" (network io, disk io, dynamic/shared libraries, ...).
checking what's different from one emacs version to the other.