Yes, Graybeard is right. It's a factory ported barrel and slide.
I've shot the 23 against the 23C (mine) - which is a 40 S&W in the same size frame as the 19 - with the same ammo. I'd guess the gun is a little "flatter", but not by much. IMHO the 40 with heavier bullets and the 9mmP don't really respond to a comp like a 38 Super or similar would. So does it help? Yes. Does it help a lot and is it necessary. I'd say no to both and the blast is more noticeable.
I bought a 23C when I was younger and more stupid (still stupid, but less than then
). The marketing sucked me in and they had just become available here. I do not like the idea of the blast, noise or the flash for defensive purposes. Shooting the pistol in a car for example across your body could direct blast towards your face through the top of the slide. I'd not do it on a defensive pistol again....
If our licensing process here was easier, I'd get a standard 23.
Then to confirm, the 19 is more "compact" than the full size 17. The 26 is more "compact" still. All are 9mmp.