The balance is very different, the SH is blade heavy so it will be more powerful in a swing, but generates more wrist strain in use. The ATAK is neutral so has the opposite set of properties, much less power on the swing, but less hand fatigue in general use. However you can choke up on the SH to reduce the torque and thus do precision cutting with greater ease, you can't however as easily choke back on the ATAK to increase power in the swing. The grip isn't designed to be stable in that configuration.
The blade steels are also very different. The SH is very strong, yet still tough , abrasion resistant and decently corrosion resistant. It is also fully hardned. McClung differntially hardens his larger blades, and thus the ATAK will be weaker because of it. His edges are also much easier to break apart, and the spine can be impacted easier. Both of them will offer solid edge retention in light work, the SH will have the advantage in heavy work because of the greater durability.
The handle on the ATAK is well shaped and generally accepted as very ergonomic, but at the same time a little slick. The SH's grip doesn't fill the hand as well, but it much more secure both forward and back (stabbing and pounding) because of the talons. The point on the ATAK is slimmer than on the SH so it will offer greater penetration, but much less strength, the latter will be compounded by the softer steel in the spine.
McClung's kydex is as good as any I have seen, and better than most. Busses sheaths are solid as well. Though if you like Kydex, McClung probably would have the advantage here.
-Cliff
