Are they a worthy addition to a Gen 5 G17?

They're a quality barrel, at least based on my experience with an early Glock 20, where I used the KKM for the improved case head support and ability to use large quantities of lead bullet handloads.

Having said that, I doubt that a KKM will provide any noticeable advantage over your factory Gen5 barrel.

I have a KKM barrel in a G17, and KKM barrels in several dozen other pistols.

KKM barrels are good; I've used them for conversion barrels a number of pistols; G35 shooting 9mm, for example, or a .40 barrel in a G32 when it's cheaper to shoot .40 than .357. I put a .357 barrel in a G35, runs like a top.

In a Glock, if you're shooting a lot of lead, some prefer the rifled barrel vs. a poly barrel. The big difference you find may not be accuracy so much as longevity.

All my KKM barrels seem to be just fine regarding accuracy. I've had no function issues with the KKM barrels. To get the best accuracy, a fitted barrel, checked for function, will offer more than a drop-in barrel.