This is a distinction without a difference. In terms of mechanical engineering and functionality, the Sig Sauer version is comparable to any number of other semi automatic magazine fed rifles. These rifles are perfectly legal and very popular.
I may or may not have a Remington 700 bolt action rifle that fires the exactly same ammunition, but only holds five rounds and must manually eject an expended cartridge and load a new round by manipulation of the bolt. The effect on the human body when hit is identical. Those clueless politicians and similarly low information media types would call what I may or may not have a “deer rifle” while the other would be called an “assault rifle”. I would not recommend the Remington 700 in .223 caliber for deer hunting and I would never recommend civilian AR-15 type rifles for use in military combat assaults. The differences are essentially cosmetic.
During the three hours that elapsed between the shooter first entered the Orlando club and when the SWAT team executed their breach, killing the shooter, either weapon discussed above would have been more than adequate to kill 49 unarmed citizens. In fact, a .69 caliber Charleville flintlock musket commonly used by our Revolutionary forefathers would have served the same purpose quite well. However, if anyone in that nightclub had been armed with a revolver or a modern semiautomatic pistol, they could have defended themselves and one or more of them would have killed this maniac before the slaughter got to these monstrous numbers.
My favorite comparison:
Both are 5.56mm caliber items. Both use the same magazines (PMAGs, steel, etc). Both have the same operation mode (semi-automatic). Both have 16" barrels and the same lethality.
One is evil; the other is perfectly acceptable (looks like a deer rifle).