The message
from The Natural Philosopher contains these words:

I have found the BIT quality to be the key thing, followed by a good
hammer action.

I've found that pneumatic SDS drills (are there any other sort?) will
sail through concrete no matter how cheap the bits. "Impact" drills
struggle no matter what bits you put in 'em.

--
Skipweasel
Pay no attention to that man behind the curtain.