Reminder: Kragg's major criticism about Thorek in one of the earlier K8P updates was that Thorek was trying to be a politician and a runesmith at once, not giving fully into either.
Which also ties interestingly into Kragg's philosophy about the secrets of Runes; It doesn't matter what knowledge is lost with his own death, he will flat out refuse to teach anyone he doesn't consider worthy of the art. And that is fine for Kragg, since in his hyperfocused specialization he has achieved such skill and experience (and age) that he can just ignore any opinions to contrary with no personal repercussions.
Where indeed it seems Thorek has a slightly more flexible mindset (for several centuries old dwarf). Which he probably needs, since he hasn't chosen to become so purely focused on only and exclusive the art of runes. Which likely also explains why he might be or straight up legitiately is a worse runesmith than Kragg in terms of absolute skill even when accounting for the age difference: Thorek, for better or worse, has chosen to use time that could be spent on understanding runes to instead meddle on other matters. Which has its own advantages, but I fully understand how someone like Kragg - who is entirely commited to the purity of his art to a degree even above other runesmiths - sees it instead as faffing about. Nor is he focused on becoming a military leader, or a diplomat or whatnot exclusively either; he could become quite good at anything he chose to be, but he refuses to fully commit to anything in particular.
Hell, theorizing further, it might be that Kragg sees Thorek as having given up. I mean, if the goal is to preserve (and best scenario, rediscover) old secrets of the runesmithing arts, Kragg is straight up more capable. He just won't teach those secrets forwards without a worthy apprentice, and lack of a worthy apprentice is to him no reason to lower the standards; it is merely yet another sign of a decaying dwarf civilization. Essentially, lamentable but apparently inevitable since worthy students just aren't to be found.
Whereas Thorek is faffing about with things other dwarves could do, wasting time on pursuits that aren't about the ancestors and ancient runelore. And if you don't care about those things exclusively above all else, why in the name of gods become a runesmith at all?
Which one is one the whole better for dwarven society in the long term? Probably the path of Thorek. Which one is more likely to bring back a faint shadow of glimpse of the splendor and heights of the gold age dawi civilization ? Probably Kragg, actually, provided he lives long enough.
And with his death, the secrets would be lost again.
So to summarize Kragg is the better Runesmith, the better dwarf by the tradtions of Karaz Ankor. the trouble is those very traditions are a major part of why Karaz Ankor is dying. Kragg's failings are not his own they are those of his society which he has taken on by being an exemplar for good and for ill.
That's the sad thing is.
When Kragg dies, it not just his secrets, and knowledge, but a little bit more of the Old Golden Age Dawi most of the remaining Holds are so obsessed with reclaiming that lost glory of Old Karaz Ankor.
It the same issues with the Slayer Cult. You are always losing the most promising Dwarfs to the Slayer life and the 'good death' that awaits them.