So who would win in a fight? Here's some information on the characters' powers and abilities:

Hulk
The Hulk possesses the potential for near-limitless physical strength depending directly on his emotional state, particularly his anger. His durability, healing, and endurance also increase in proportion to his temper. The Hulk is resistant to most forms of injury or damage. The extent varies between interpretations, but he has withstood the equivalent of inner solar temperatures, nuclear explosions, and planet-splitting impacts. He has been shown to have both regenerative and adaptive healing abilities, including growing tissues to allow him to breathe underwater, surviving unprotected in space for extended periods (yet still eventually needing to breathe), and when injured, healing from most wounds within seconds. His powerful legs allow him to leap into lower Earth orbit or across continents, and he has displayed sufficient superhuman speed to match Thor, or the Sentry.

Juggernaut
Juggernaut is a magical avatar of the supernatural entity Cyttorak; he gained superhuman powers through the transference of mystical energies from Cyttorak via a magical gemstone, the Ruby of Cyttorak. The ruby bonds to his soul and alters his being, a scale of power rivaling that of Thor, the Hulk, and the Thing. In an incredibly weakened state, he has been strong enough to rip off and wield the entire corners of buildings as giant weapons. Besides giving him superhuman strength, the mystical energy of Cyttorak grants the Juggernaut completely inexhaustible stamina, and the ability to survive without food, water or oxygen. He possesses tremendous durability, and can further protect himself through a practically indestructible force-field. The Juggernaut has the mystical attribute of being physically unstoppable: Once in motion, virtually no obstacle or force is able to impede his movement.