Difficult to compare them yet. Jack proved his individual strength and endurance when holding his ground against Neko & Inu each for 5 days, characters of the strength to make Bege flee after calling them "monsters". Cracker proved his individual strength and DF / Haki skill by so far easily handling Gear 4 in a way Mingo could have never done.
Jack is more durable, Cracker is smarter. I would imagine Neko & Inu's individual strength to be comparable to Gear 4 Luffy, maybe a tad weaker, so what Cracker did is impressive. Tho thta may change once we see the rest of the fight in the Manga.
So far I don't see anything that would make me say 1 is decisively stronger than the other to win this fight. But I'd love to see it. Yonko Commander vs. Yonko Commander, a huge mammoth against Cracker's army of Haki enhanced and insanely tough biscuit soldiers.