For defensive use, the CX4 is, for me, a better choice, compact, faster to get on target, softer shooting and (in my experience) more accurate. Another significant advantage from my perspective is it uses the same magazines as my PX4 and/or 92 series pistols. One other major consideration; my wife is left handed and setting up a CX4 for a lefty is quick and easy. The 92 Series magwell CX4 is lefty, Susan prefers a VerTec frame M9A3 over a PX4. I'm equally comfortable with a 92 or PX4.
I have had 2 Scorpions, one pistol and one carbine. Both were well made and reliable, but didn't work as well for me. Ended up putting way too much money into the guns to get them to fit and function well for me. If they used the same mags as a 75 series or P07 pistol, I'd likely still have one.
I've had two 9mm AR platform guns, if I were into competition shooting, I'd probably still have one. I built one to use Glock mags and one for Beretta 92 mags.
I've also had a Ruger PCC9, it's probably the most accurate and softest shooting of all the 9mm carbines I've tried. Mine was setup for Glock mags. I gave the carbine and a Glock 19X, I had, to my son in law. My daughter likes shooting the PCC9 and having mag compatibility with her Glock 19. I don't like how Glock pistols fit me and wasn't going to keep the carbine and pistol pair.
All of that said, if I could only have one handgun and carbine pair it would be my 4 inch S&W 586 (perhaps my Kimber K6s Combat or 4 inch S&W model 66) and Henry X Model 357. A bit more accurate, way more power, vastly more flexible, more fun to shoot, and can be used for hunting and feral hog control.