I'm not about to get into the "Brand X vs Brand Y" debate .... that discussion too often takes on religious overtones.
I do have some hammer-drill observations, though .....
My cordless DeWalt does seem to have the right mix of rotation / frequency / amount of impact to drill effectively in brick, block, and softer concrete. This contrasts to a corded Skil I hadmthat seemed only to make more noise on the 'hammerdrill' setting!
In a similar manner, a small Bosch (corded) I used long ago wasn't very good with super-hard brick, while the Hilti (of similar size) drilled very well.
The corded Milwaukee I also have to say I've had decent results with.
Now... as for 'different brands that come out of the same factory'.... I've had both the DeWalt and FireStorm (Black and Decker) cordless reciprocating saws. Let's see ... $280 for the DeW, $90 for the FS. You think there might be a difference?
The FS lasted about six months, before the plastic gears within were completely stripped. The batteries took an hour to charge, were vulnerable to overcharging, and crapped out after two or three cycles. The almost identical (in appearance) DeWalt batteries last me about 18 months (on average). Differences were also felt in weight, balance, and vibration.
Carry the same comparison over to drills. My DeWalt Drill spins quite a bit faster than the B&D. There also seems to be quite a bit more torque in the DeWalt ... ironic, again, as the batteries are almost interchangeable.
Indeed, I made a slight change to the B&D so that they would accept the DeWalt batteries ... so my comparisons are based upon the tools alone, and not the battery!
The biggest problem with hammerdrills is the temptation to ask too much of them.
I limit my use of the hammerdrill to 1/4" holes, or smaller. Larger than that gets a roto-hammer.
Some smaller holes ... such as holes for tapcons (the blue screws) into concrete are also very likely to be made with the roto-hammer.