Hammer Drill vs SDS Rotary Hammer
A hammer drill adds percussion to a standard chuck for occasional masonry. An SDS rotary hammer uses a different bit-retention system built for solid concrete. The bits are not interchangeable.
A hammer drill adds a percussive hammer action to a standard chuck-based drill for occasional masonry work (anchors in brick, block, or mortar) — it is still a chuck that grips round or hex shanks. An SDS (rotary) hammer uses a completely different bit-retention mechanism (SDS-Plus or SDS-Max, a slotted shank that locks and free-floats in the tool) and a true rotary-hammer mechanism built for repeated drilling in solid poured concrete and light chipping/demolition. The bit systems are not interchangeable, and a hammer-drill will struggle or fail at tasks an SDS rotary hammer handles routinely.