Another quesition, I'm afraid.  In the main, I get the impression :w
macros should be avoided if there is an equivalent :c or :n one.
However, although there is \chk_exist_cs:c, the is no mention of \cs:c
(= \@nameuse).  I'd have thought this would be a good idea, or is there
a reason for avoiding this?
-- 
Joseph Wright