I would never advise the northern route in winter. The Sierra de Loarre would likely be impossible, and the Sierra de la Pena certainly would be. Professional equipment and support would be necessary, and I doubt that the authorities would permit it. As well, there are significant stretches into without much population and, should the weather turn very foul, the open fields could be unpleasant to dangerous.
I have not tried the Ebro route. Last year, I stood at the intersection of the two west of Tarrega and flipped a coin. North it was. From the Amics handbook, which you should not think of walking without, there are many more albergues and other accommodation. If you are walking in winter, I would suspect that many of the albergues will not be open, but there are always fondas, hostales and rooms above cafés. The Amics in Barcelona should be able to give more specific information on this.
