Use or avoid toll roads

I have read many discussions on travelling through France to Spain. For a first timer like me do you advise to use toll roads or not. I plan to drive with caravan from Calais to Mercia in Spain. I have looked at the routes on Viamichelin and either using toll roads or not the distance involved is about the same. There is a cost difference but that is not my main concern. I want a route that is east to follow. Please advise.