tools
When using Allen Wrenches (Hex Keys), I've always held onto the long end because I figured it gave me better leverage and torque. Sometimes, in hard to reach places, I would hold the short end.
Then I saw these ball end hex keys. They claim that:
The advantage is that their ball end make it easier to slide the
wrench into the receiving slot.
In my opinion, they've put the ball end on the wrong side.
Have I been using these incorrectly my whole life?
Cordless
I re-read your question and saw it said cordless. I don't have a cordless but this website rated the Milwaukee 0824-24 V18 Lithium-Ion Hammer Drill Kit as the best. The Hitachi DV14DL 14.4-Volt Lithium-Ion Cordless Hammer Drill is another quality product available for about the same price as the Milwaukee drill.
Cord
I have this one and it works pretty well - Hitachi 5-Amp 5/8" Hammer Drill
Don't forget to buy a good hammer drill bit if you are doing true hammer drill work! Non-hammer drill bits will break. I suggest carbide tipped drill bits for this task. The smaller the drill bit though, the faster they break - carbide or not.
This is just an Allen driver bit - you use it with a detachable head screwdriver.
Best Answer
The ball end of the wrench fits less securely in the socket than the squared off end so you can't apply as much torque without risk of the wrench slipping or stripping the bolt head. So it makes sense that if your wrench only has the ball end on one end, that it's on the long end so you have to use the short end to hold the wrench to limit how much torque you can apply. That preserves the more securely fitting squared off short end for applying the most torque on the fastener while you hold the long end.
Its ok to use either end of the wrench on the fastener and sometimes space limitations will force you to use one or the other.