I have completed both routes and have done some portions of both twice.
If you speak some French, I would recommend the Le Puy route because most of the people whom you will encounter on it will be French. Your travel time, because you will be in France, will be minimized and it is a wonderful hike with, IMO, better food than you will find in Spain. It is also a little more expensive.
If you don't speak French and your trip begins in France, take a train and bus to either Navarrenx or Saint-Palais. Both are in France and from there you can walk to Saint-Jean-Pied-de-Port on the last few stages of the Le Puy route. Then I think you will have time to walk the
Camino Frances in its entirety. How long you will need depends on how much distance you will cover each day and how many rest days you might need or want to take. This option allows you a few days to get in shape before hiking over the Pyrenees to Roncesvalles.
Good luck. You cannot go wrong with either choice.
Tom
P.S. I forgot to mention that no sleeping bag is needed on the Le Puy Route, just a sleeping bag liner. In Spain you will need to carry a sleeping bag. If you were to start in France (without a sleeping bag), you could buy a cheap lightweight bag in Saint-Jean-Pied-de-Port.