They both could have approached this in perhaps a different way but it includes a variety of improvements. Mil Spec means both that they have improved performance and that it has improved resistance to environmental factors. More relevant perhaps is that it is a recognized standard of quality and from a purchasing standpoint allows those who adopt it to buy from a wider source of vendors where they **know** that the product meets their goals even if it's more than they need. After all what giant electronic parts supplier doesn't want a piece of the multi -trillion dollar military market.
So if the question is, does passing **all of the tests** required actually improve the user experience, I would say "no". But if your asking if the ones that do matter have an impact, I would say yes and by buying Mil Spec, they don't have to run around with a list of important criteria that do matter and ask suppliers to "make this special for us".
I'll give you an example of this kind of logistics. I was involved as an expert witness regarding a child being injured on one of those indoor 3 seat merry go rounds. The mother claimed that the unit just started up "all by itself" when she was no where near the wall mounted button that started the ride.
There was a $250 option to get the ride with a handheld remote. It tuned out that every unit shipped with a receiver in the base of the ride which would receive the handheld remote signal. All you got when you added the option at a later date was the "clicker". The part in the base of the unit was more expensive than the "clicker" but for logistics reasons (inventory management, etc), they shipped every unit out with the receiver inside. As a result, since they operated at the same frequencies, the ride could have been started say by a garage door opener clicked by a dude parked right outside the window in the fast food restaurant while getting his sunglasses off the visor. But the relevant issue with regard to our discussion is ... they added a part and "ate the cost", because that cost was less than managing multiple model lines.
But as you brought up the 970, we'll use that as an example:
http://www.bit-tech.net/hardware/graphics/2014/09/19/nvidia-geforce-gtx-970-review/4
The power delivery is the best of any here; it's a 6+2 design. Further, MSI uses its own improved components for both the GPU and the memory power phases. The components are referred to as Military Class 4 since they meet MIL-STD-810G regulations. Specifically, we find Hi-c CAP and Solid CAP type capacitors and Super Ferrite Chokes, which are designed to provide higher stability, lifespan and efficiency.
Looking at the previous pages
Examining the PCB reveals a 4+2 phase power design – four phases near the rear I/O for the GPU, and two in the bottom right corner for the memory. This is a slight upgrade from the 4+1 stock specification but unlike MSI and ASUS, EVGA does not use any specially crafted components.
We also find a 6-phase power delivery system for the GPU, a 50 percent upgrade from stock specifications. It also uses ASUS's DIGI+ VRM controller for precise, digital voltages, as well as high quality Super Alloy Power components for buzz-free choke operation, longer capacitor lifespan and MOSFETs with a 30 percent higher voltage threshold than standard. Sadly, the memory has not been granted the same treatment. It is fed by a single phase found at the other side of the PCB, and this one does not use any special components.
Now after reading that ... before going to the performance / testing overclocking results page (here factory presets are taken out of the equation) , you have already been handed a "spoiler" in that by reading the above, as well as the differences in VRM / Memory cooling, you know exactly who is gonna finish on top. Asus went "half way" with the 970 and given how well the two cards sold in the marketplace, now they seem intent on going the rest of the way. from what we see here. As usual, the EVGA SC used the standard reference PCB with no improvements, tho they did manage a higher core OC than Asus did, Asus had higher memory performance than EVGA tho.
The environmental factors in this package include a hardened board w/ steel reinforcing to reduce socket pullout as well as additional resistance to heat and humidity, the latter being of significant interest to water coolers. In addition, during hurricane Sandy, a tree came thru my son's window resulting in a rainstorm in his room. His puter was right under the window.
He got it out of there but it got a good bath before he did so and got some plastic over the window. Granted not exactly an every day occurrence but the spilled soda / coffee left on top of the case and the water gun battles is not exactly an isolated thing w/ 3 teenage boys. Nothing is going to stop a direct shot of liquid into a socket but I do like knowing that some level of protection is provided. Living close to the water, you can sometimes go to sleep with a nice dry cool breeze at night and then wake up to a damp / wet surfaces on furniture from morning fog.
But again, I would imagine the economics of the change was of as much significance as the performance and quality improvements ... my thinking is that it may cost more to make Mil Spec compliant components that pass 20 criteria but economies of scale bring the price down. On the other hand, buying components that past say just 10 of those desired criteria, is a smaller market for the suppliers and the logistics / soft costs of that separate production run bring it in close to the same, or perhaps even more expensive, than the Mil Spec stuff.
I also think it's a good move for Asus from a mindshare perspective. After completely dominating the market for years, their market share started slipping with Z87. The company took a turn it seemed with increased focus on margins and less on having the top dog in each price niche. When you compare similar featured boards side by side, looking at features offered and quality of components used, you were paying significantly more for the Asus board, than the competition and the competition of late was edging them quality / performance wise in a few categories. For example, recently we saw with Z170 that almost every Asus board under $150 came with a substandard audio subsystem (ALC 887 / 892) while Giga and MSI were offering ALC 1150 down to and even below $100. With Z87, we had sites like Sins hardware were showing us that Giga was leading in the power delivery on MoBos, MSi was getting kudos for GFX card cooling innovations and winning head to head performance battles. So making this move shows the enthusiast community that Asus is serious about regaining that mindshare of Asus not taking a backseat to anybody with regard to having BAT (best available technology).