i don't know how the current state of juggy differs fro the early 90s state (when i stopped reading comics) but thor did stop yes STOP juggernaut with mjolnir. he channeled the god-powers or something through his hammer and stoped juggy cold. the person who mentioned something about different writers has a very salient point. the extent of the powers of these characters (and any caveats therein) can change significantly with different writers.
so we are really talking about ideas of these characters, but how do we define them?
1) juggy as a being completely immune to any type of physical force, but with a limited strength and no non-physical abilities (like energy projection).
2) hulk.. well, i'm not sure which hulk you guys are talking about, the angry hulk or the professor hulk. either way it's important to note that the hulk derives his form/power from a combination of radiological mutation and psychological trauma. the hulks powers can chage dramatically depending on many things. doc samson, when trying to cure bruce banner of his mental disease encountered all of the hulk personalities insibe banner (one called 'monster hulk' was potentially the most powerful/evil of all, iirc. samson's machinations managed to turn banner into the professor hulk, which, as i mentioned in my last post, juggy managed to defeat (partially by tricking the hulk).
the point is neither character is really all that fixed, but the hulk seems to have more wiggle-room in terms of his power, due to its partially psychological source. this allows writers to factor the limitless potential of the 'mental plane' into the hulks power, and i think it may be incorrect to assume that the hulk could only exert pure physical force when facing a dangerous foe like the juggernaut.