As others have said, a framing hammer is a specialty claw hammer.
So what makes it different? First, weight. A framing hammer is typically 20-32 oz, compared with 10-16 oz for a "normal" household claw hammer. That helps it pound large nails in only a few blows. Related to that is the much longer handle on a framing hammer.
Second is the face of the head: it's waffled to prevent slipping off the nail head, helping prevent bent nails. A regular claw hammer will sometimes have a textured face but not nearly as pronounced, and the face may also be smooth. A regular claw hammer often also has a domed face to allow a skilled hand to sink a nail below the surface with minimal surface damage: that's a feature you won't see on a framing hammer.
Third, the claw is straight since it is optimized for prying boards apart. A regular claw hammer is optimized for pulling nails.
If you're only building a garage, I'd recommend using your regular hammer rather than buying a framing hammer. (Or best of all, just go rent a nail gun!). For inexperienced carpenters, the time spent hammering will probably not be what slows you down. Also, the framing hammer is tiring enough that after a couple hours you may actually be faster with a smaller, regular claw hammer.
If you do get a framing hammer I recommend a lighter one. You'll work faster when you use it, you won't lose much power over a heavier hammer, and you'll feel much better on the second day. In 2010 if you hammer enough that a 32oz hammer makes a difference versus a 24oz hammer, you have a nail gun anyhow.
Most driver bit sets come with a 1/4" square drive adapter (my small Milwaukee set also came with a 3/8" drive as well, though I don't know if that's common). With that one bit, your driver is instantly almost exactly the same as a 1/4" impact wrench. You'd have to look at torque specs to see if the models you're considering are comparable, but I bet they are. Those little impact drivers have come a long way -- battery life is great and the torque is hard to believe.
I'd only consider a square drive impact wrench for heavier automotive (or other mechanical) use, and only in a larger size like 1/2" so it can provide some real help in removing tough fasteners.
Best Answer
Compressing gas makes it hotter. This is the principle exploited by fire pistons to set fire to things. It is also used in a Diesel engine to ignite the fuel.
CCASA 3.0 Chocolateoak
For an ideal gas P V ∝ T. As you increase pressure (P) the volume (V) reduces, however air is not perfectly compressible, so when you double the pressure, the volume is reduced by less than half, therefore temperature (T) must increase.
Another way to look at this is that your compressor is doing work on the air. Work is energy, some of that energy ends up in the form of heat.
Also, any kind of motor (electric or other) produces heat.
Pipes made of metal are good at conducting heat into adjacent hoses and fingers.
The opposite is also true, the reason that CO2 fire extinguishers have a plastic guard or handle on the nozzle is to prevent your hands freezing onto the outlet pipe as you discharge the gas - allowing it's pressure to decrease as it leaves the container.