"Dave Plowman" wrote in message

I reckon SDS works better in 3 ways:-

The lower mass of the drill against a drill/chuck combination makes the
impact greater even if the 'hammer' were the same.

The impact mechanism is better - a hammer drill uses a ramp mechanism,
and there's a limit to the acceleration that can be achieved. IIRC, SDS
uses a pneumatic system.

The SDS bit can't slip even slightly in a rotary direction.

Feel free to add or subtract. ;-)

Excellent point. Had to laugh at yet more powerful, sorry yet more cells,
30V cordless keyless chuck drill being demoed live on QVC a week or so ago.
Couldn't drill the concrete or cast iron because the bit kept sticking even
after attempt at really tightening chuck. Quick cut to VT. A mid-range SDS
drill can be had for about the same cost.

Alan