Hulk is not not unkillable He is however immortal.
He can be killed by sufficient Force .
Juggernaut is immortal and unkillable by physical force therefore he would out last the Hulk in a straight up hand to hand fight with no retreat for either guy may take years but Juggernaut would be the last man standing.
"However, reabsorbing the energies that the fake gem had stolen, Cain also was infected with an evil spirit residing inside it. It possessed the Juggernaut and, more powerful than ever, used him to smash his way through the barriers between dimensions to get back to the place it came from and conquer it. Black Tom and the aliens living there summoned the X-Men to their aid, as the Juggernaut had grown bigger and more powerful each step of the way. Only after Xavier and Wolverine entered Cain’s mind and helped him to overpower the evil influence did the threat end. The Juggernaut shrank to regular size and returned home. [X-Men (2nd series) #88, Uncanny X-Men #369]"
Clearly Hulk isn't the only one who is able to smash through things that well...shouldn't be smash-able. So that arguement is futile.