I have been running Ruthenium plugs in my 2015 5.3L for over 30,000 miles now. Noticed improved fuel mileage, smoother idle, and cleaner burning right after I put them in. No problems at all so far, and I just checked them recently and they are very clean for their age. Will probably replace with the same thing in a few more thousand miles.
Also as others above said, guess who makes the ACDelco-branded plugs? Yep, NGK. They are built to specs that GM lays out, which aren't always based on the best for the life of the engine (they usually are spec'd to meet some government requirements). That's not to say the OEM plugs are junk, they will work fine for the application. But paying more for the Ruthenium ones will get you some improvement, it's just up to personal preference.