I have 3 pistol caliber carbines:
One's a Marlin Lever Action in .357 Magnum. Great rifle.
One's a Hi-Point 995 in 9MM. This is one of the most fun guns I have ever owned. It's scarily accurate and it does things that no 9MM Carbine should be able to do. The stock is long enough that its wierd looking style is actually pretty comfortable. The only thing that stinks on this is the 10 round magazine.
The other's a KT S2K in 9MM that takes the Glock 17 Magazines. The 33 round G18 magazines are impressive to shoot. However, the stock is short for just about everyone, including females, even with the 1.5 inch stock extension. Just be prepared to hunker down and hold it REAL close. The nice thing about this one is its ability to fold down and go inside my range bag. Cost $159.00 8 months ago.
If you haven't thought about it, consider an M-1 Carbine. The cartridge is a rifle cartridge, but it's so downpowered compared to a real rifle cartridge, it might as well be a pistol cartridge fired out of a rifle. It's been in use for over 60 years and is light enough that anyone can handle it. Throw in the 30 round magazines, and you have a nice little rifle that's accurate to 100 yards or so. Cost: 350.00 or so. I traded another rifle of mine for this one.
I have fired the Beretta CX-4 and find that it really doesn't offer anything that the other two inexpensive carbines already offer.