There are lots of differences in general between genuine MIL-C-5040H paracord and commercial grade paracord. However, as to the high grade commercial there’s one variety where arguments have been made that it is even better than MIL-C-5040H.
There are maybe five commercial paracord suppliers that I’m aware of that consistently carry “high grade commercial” paracord — i.e. paracord that you can depend on — and I don’t know but I suspect its because these suppliers have had long relationships with their manufacturers. One thing these top suppliers have in common is that they’ve all been dealing with paracord for a decade or two. Keep in mind that the commercial versions have never been officially tested — nor have they met any known (as least known to me) manufacturing standards whatsoever. (The only exceptions are the actual manufactures of parachute shock cord - which is great stuff.)
As to the other 99% of what goes for “Mil-Spec” commercial grade, it is in my view, junk, and as to Type III, you’d be lucky if the break strength is anywhere near 550 - usually closer to 200 to 400 pounds. However, as to perhaps’s 90% of my own needs, I’m perfectly fine utilizing the junk, even into the unknown.
By the way, the actual break strength of MIL-C-5040H of Type III is about 750 pounds even though its officially rated for 550 pounds. Similarly, the actual break strength of Type IV is over 1,000 pounds even though the government rates it at 750 lbs. During manufacturing of MIL-C-5040H testing is done as to every aspect of stretch, elongation, ratios, break strength, etc.
It was the day before Katrina made landfall that I was injured due to the my own overestimation of the break strength of commercial cord. To say this happened at the worst possible time ever would be an understatement. This was truly the only time break strength mattered (as in life and death) to me personally. I was aware paracord stretches a lot and had compensated — just didn’t think it would break. It broke.
Ever since, as to paracord for the kits for my family in particular, I’m committed to maintaining them with genuine MIL-C-5040H cord (Type II especially as to the small kits) and other cord (particularly low stretch Dacron cord) that I know to be predictable.
Here’s an excellent article about MIL-C-5040H vs. commercial cord that was posted on the Consumer Planet blog about a year ago:
http://blog.consumerpla.net/2011/03/550-paracord-universal-cord-tool-cool.html