I think when these combat threads are created a few more details needs to be chosen, i.e. which powers are used, where is the combat, etc. . .
Generalizing these combatants is difficult, but here it goes . . .
Silver Surfer wins if all powers are used (and he had no moral resistance to using them), Sub-Atomic break down kills anyone in DBZ . . .end of story.
Now in terms of straight combat ability (Resistance to Damage, Amount of Damage Done, Energy Projection, Speed) DBZ wins straight out.