It's close, but I went with Hull.
Their offensive stats are fairly close. They scored nearly the same number of points (1,398 to 1,391 in favour of Kurri), in nearly the same number of games (1,251 for Kurri and 1,269 for Hull). But there are two important factors that favour Hull. One, he spent much more time in the Dead Puck Era, where scoring was lower. Two, Kurri benefitted - though the extent is debatable - by spending his prime playing next to prime Gretzky.
Both were great playoff performers. Kurri scored about 24% more on a per game basis. That's significant - but the same two qualifications I made above also apply here. (Also note that Kurri only played 54 playoff games in thirties; Hull played 130). I'd still rank Kurri ahead as a playoff performer, but it's much closer than the raw numbers suggest.
Kurri was clearly the better defensive player - no debate there.
Ultimately I'd rank Hull ahead because he had the higher peak, and had better longevity. Kurri never had a stretch as dominant as Hull's run from 1990 to 1992. On top of that, Hull simply remained relevant for longer. Kurri scored more than 60 points in a season just twice after age 29 (when he was 32 and 33). Hull did so at ages 31, 32, 33, 36, 37, 38 and 39 (and he easily would have at age 30 - lockout year).