Overall, I would say that the Northern Renaissance was less secular than the Italian Renaissance. The Northern Renaissance was also less dramatic in its changes and the changes that did happen seemed to happen at a slower pace.
The most important difference comes from the fact that the thinkers of the Italian Renaissance had access to lots of texts from the classical period. By looking at these, they came to believe in the idea of humanism. By contrast, the Northerners did not have access to these texts. This meant that they looked at the Church and started to think about reforming it.