The only way a 9mm Carbine makes sense is if it shares magazines with your chosen pistol.
If you have a Beretta, then get the CX4. If you have a Glock, then use an Olympic 9mm Carbine, or build one with a Lone Wolf lower to make a Glock compatible carbine.
The Marlin Camp 9 used S&W Magazines?
If you are doing a "SHTF" kind of setup, make your gear count....
Otherwise, there is precious little advantage to a Pistol Caliber Carbine, IMVHO.