The efficiency will obviously be dependent on the length of the key list argument, as those solutions which iterate over the entirety of the key list will be performing assoc queries on a null list if one of the keys is not found.
Yup, thats why unstoppable iterators like
foreach mapcar repeat, although perform faster (cause the lack of a test function expr to mid-stop the iteration)
iterators like
while vl-some vl-every, are more efficient - so they won't process the whole list (but will require the test function expr).
Just to clarify for anyone.