Both are strong & will most likely be the strongest pirate captains of their generation alongside Luffy but neither are PK material imo. Particularly since they are both significantly lagging behind Luffy in almost every single category u can possibly imagine atm. Compared to characters like BB, Luffy & the Yonko, they just don’t stack up. That said, both are still relatively strong & Oda pitting both against a Yonko for their climax is testament to that. So I think both are strong candidates for ‘Yonko’ spots EoS ^^.
With regards to a comparison btw Law & Kidd. From a showing perspective, Law has been a lot more impressive than Kidd & Law also has a significantly better DF (at least from what we’ve seen so far. Will be interesting to see whether Kidd’s df is a special paramecia in which case there’s a lot of potential there). That said however, even with Kidd being so meh post-ts. I think there’s a good chance he’d have some pretty good feats by the end of this arc. Apparently, he injured a sweet commander + he also apparently has CoC & is currently faced off against Linlin with Law atm so Oda’s set him apart from the rest of the Supernova save Luffy, Zoro & Law.
Portrayal wise I think both Kidd & Law are equal. One could argue that Kidd has CoC but on the other hand Law is a D & Kidd isn’t so there’s a balance here ^^
Personally, if I had to say who is stronger tho, it’d choose Law 10 times out of 10 reason being that all both really have going for them atm from a strength perspective is their DF prowess & Law’s DF abilities are just so much better than Kid’s, Support-wise, Attack-wise etc. So Kidd really has to show a lot more with his DF. Stuff like repel isn’t going to cut it & that ability is too circumstantial. If Kidd fights in a place without metal (a desert for example), he’s fck’d at least based off what we have seen so far