If your job includes drilling concrete or other masonry you should try the rotary hammers. Using this type of tools will make you to lose interest in usual hammer drills and use the rotary ones.
These rotary hammers have great results for heavily packed concrete with aggregates.
When buying a rotary hammer you should take into consideration some criteria. One of the most important is the power of the drill. You can get useful information from the descriptions provided by the manufacturers, but the best way to do this is by reading the opinions of those who already used it.
Also speed makes great difference between these hammers. Most of them are designed to work just fine without putting pressure on them for more speed. Sometimes pressure can can be damaging.
Too much vibration can make a rotary hammer to hard to use. Before buying the tool, you should find tone with the least vibrations. This will help you not to get tired before finishing the job.