As others have said, it depends on what part of "The North" and what you like doing...if you like edgy stuff, Manchester will suit you, and parts of Newcastle (though overall it's a bit more laid-back than Manchester most of the time - yes, I do know both cities).
If you like peace, quiet and empty beaches, head for Northumberland, anywhere north of Newcastle.
If you like things to do for kids, then Leeds, Manchester, Liverpool, Newcastle will suit you.
If you like driving, Northumberland will be fine; central Manchester, not so much. If you'd rather get around by public transport, Newcastle will be perfect; Manchester has a pretty good public transit system too (though locals may disagree, if they compare it with most other places they'll realise just how good it is). If you like castles and interesting architecture going back to the Romans at least, Newcastle and Northumberland.
Lots of factors to bear in mind!