travel time

Well, "best" is always subjective. Not sure what you mean - fastest? cheapest? most scenic? - do you want to travel by car? train? plane? open to all options? When are you traveling (time of year)? You need to be a little more specific and there will be people here who can help you.

Fly to Rennes. Take the bus the rest of the way.

Anything else is much longer and price will be a wash considering the extra meals required during the trip.

I looked at some dummy fares and if cost is part of your "best", I would fly to Paris and train to Bayeux - much cheaper to fly to Paris than to Rennes but would take a little longer. So, in the end, it depends on what "best" means to you.

Try rome2rio.com to see your options.