Car, Train or Bus???

I think you will want a car to explore the regions beyond just the listed towns, so I recommend keeping the same car for most of the trip. Car rentals are cheaper for 7 days or more; try a price quote at AutoEurope or Kemwel. For instance, you could train to Tours, pick up the car there, and work your way south, dropping the car in Marseille or Nice, if you're flying home from the south. If you need a long train ride back to Paris, then book the ticket about 3 months ahead for best price.

Once you make it down to Provence, it's nice to have your own wheels if you're looking at driving in The Luberon or other places on your schedule. Buses can get you around (we found Avignon to be a great transportation hub for that area) but you're on their schedule and you have to know where to pick the bus up again to return or to continue your journey.

Trains (especially the super-fast TGV) can get get you there quickly and you don't have to focus on driving the whole time, but come with a price. Cars come with a price, too, including gas and tolls. A combination might work for you, if you don't wind up with the same car the eintire trip.

Do you just want to visit the 3 cities you list (Colmar, Arles and Tours), or visit the surrounding area?
I guess the latter, as 3-4 days in just each town is too long, and all places are surrounded by good things to see. Therefore you need a car.
The problem you have is that these 3 places are at opposite sides of France, Colmar East of Paris, Arles in the south of France and Tours in the west. For example, driving Colmar to Arles (according to www.viamichelin.com ):

Costs: 122.60 € with a Petrol vehicle (Toll 47.40 € | Petrol 75.2 €)
Time: 07h15 with 05h46 on motorways
Distance: 666 km with 596 km on motorways

That is a full day driving. Plus parking in all 3 off these cities could be difficult.
Thus, I would disagree with Laura. Hiring for 7 days may be cheaper, but I would suggest using High Speed trains, followed by one car-free day in each city, followed by 2-3 days of car hire to visit the countryside, then hand in the car and train to next city.

Colmar to Arles by train ( https://www.capitainetrain.com ):
6-7 hours, cost approx. €70 to €90 per person 2nd class.

Bus: No. Too slow, too uncomfortable. Too few long-distance services.

Colmar: Don't forget to visit the Route de Vins d'Alsace in your car.

I'm with Chris. Yes you'll want wheels in all of these regions. But with only 11 days you need to take advantage of the trains, which are really fast. Faster than driving.

Even so, the train between Alsace and Provence will take a good 6 hours. I'd say break the trip for a night in Lyon or Beaune (and maybe drive if you like), but that will just make your plan the more frenetic.

Speaking of 11 days: This is awfully past paced. I'd spend the largest share in the south. Maybe 2L-3A-5P, where # = nights. (So 1 full day in the Loire, 2 in Alsace, 4 in Provence. (A little chateux go a long way.)

How are you getting home? Flying from Marseilles or from Paris? If you book an afternoon flight there's a train from Provence that will get you to deGaulle by 10:30 AM.

we are flying out of Paris and have planned on getting to Paris the day before flying home. Yes, we want to see the surrounding country and not just the towns, so a car will be important. Just not sure if it's do-able going to all three regions. Would it be wiser to just do two, if so which ones? I think Provence is tops on our list. Not sure of the other two as to which is more interesting.

Do your 11 days include the day you arrive in France and the day you fly out?

Steve, the problem you have is that you have made 3 good choices, Alsace, Provence and the Loire valley. All very nice places and all different. It would be difficult to cut any one of them.
I agree with you putting Provence top of your list.

Is there any way you can squeeze 3 more days, one per location? Bearing in mind you have a full day travel Alsace --> Provence and Provence --> Loire Valley that should allow you to see some of the really great sights. In both areas.
If not, I would regretfully say cut Alsace. It is a beautiful area (even though I am slightly biased as it is local to me), and a very different area and culture to the other two, I would say Provence and the Loire valley offer more 5* 'wow' sights.

If you do do Alsace, I would say 1 day Strasbourg, 1 day Colmar and one day in the car touring the small wine villages at the foot of the hills.

The 11 days are what is available to us after taking in consideration of our time in Paris and the time to fly home again. Wish we could add more days but that isn't possible. I really appreciate the advise I'm getting. Thank you all.

With 11 days to devote to your trip, I think I would choose two of the areas. If you're the type who likes to run run run, all 3 would be possible, but you really will run yourself ragged and not get much time to enjoy. But some people thrive on that kind of fast-paced, do-something-every-second kind of pace. For myself, as I said, I would choose two; that still wouldn't be exactly leisurely, but at least wouldn't be quite so frenetic. A big part of the issue is how much time you'll spend getting between each of these far-flung areas (and Paris before and after).

You would have to count four days as basically only travel time, giving you seven days in all 3 places total. (Yes in reality you would get the odd morning or evening in one of the places before/after a long travel day, but not much more than that). So that gives you two days in say Provence and Alsace, and one day in the Loire. That just doesn't sound worth it to me.

If you pick two places, you have three days' traveling, leaving you with 8 days to split between two regions -- I.e. four days each, or 3 and 5, whatever makes sense according to your preferences.

Decide which pace works best for you!

Logistically, the best one to leave out is Alsace, based on trip times, tthough its not much better.

Aesthetically is your call.

Were in your place I would work at avoiding that last odd evening in Paris, the day before your flight home. After you settle in to the last-night hotel, it's going to feel almost like a slack day. But it could be a sightseeing day.

There are 3 ways to do that. One is to fly open jaw, but based on your response it sounds as though you've already bought your air tickets.

Another, if your return flight is not earlier than 1:30 or so, is to plan to end in Provence and then take the early train that arrives at deGaulle at 10:30 AM.

The third way is to start your trip at one of your non-Paris destinations and save Paris until the end, consolidating all your time there. For instance, you could take the train to the Loire the first day and proceed from there.

You've got a certain amount of trip time in your itinerary that is not reducible, but you do have choices about how to arrange the different bits.