Aix-en-Provence vs Avignon

They are very different. To know which is better for you, one would need to know what you enjoy seeing while on vacation. I enjoyed Avignon a lot but I like visiting sights like the Palais des Papes. My husband liked AIx because he enjoys walking around in very pleasant areas and not really seeing any historical sights and he loved the streets and fountains in Aix and its lively college town feel. Avignon is about an 1.5 hours from Marseille and AIx is about 30 minutes away by car. Maybe travel time is the deciding issue for you.

By fast TGV train from Marseille St-Charles, Aix is five to 10 minutes and Avignon is around 30 minutes. In both cases the TGV station is on the edge of the town with quick shuttle rides available. The much slower regional trains go to the town centre stations.

If you like shopping, Aix has a great, extensive outdoor marche. Not sure what days it runs on, but I'm sure you could look it up.
I've heard it is considered the best in Europe, I think this is a correct description. As another poster said, Aix is not a town for specific sights, more for strolling, shopping, eating in a nice atmosphere.

I preferred Arles to both of these, but of the two you mentioned, I much preferred Avignon. Aix was not only a bit disappointing, but it didn't match Rick's description. He emphasizes how rich and chi-chi it is, and I didn't find that at all; it's fine, but hardly the "Beverly Hills of southern France" that he makes it seem like.

Do read about each of these to see which one interests you more. And do heed the advice above about Aix and Avignon having two trains stations, one for TGV and one for regular trains. While the trip from Marseille to the TGV station is faster, you then have to take a connecting bus or train to the town center, which is more hassle and not much faster than just taking the "slower" train (or for Aix, bus) from Marseille, and having a "one seat ride" to the center.

Personally, I did not like Avignon. I found it unattractive, and thought that only the Palais des Papes was worth seeing. On the other hand, I really enjoyed Aix. I don't think we did anything besides just strolling, and going to the markets.

Have you considered Arles? I'm with Harold. We have visited all three...Arles, Avignon, and Aix. We liked Arles the best, by far. We thought the town was very pretty, and the Roman sights added to our impression. Outside of the Papal Palace, we found little in Avignon other than the bridge of my 3rd grade French class song. Aix was the most disappointing, and I couldn't say why. Nothing in particular, and nothing special either. We spent hours walking all over and the thing I most remember? Pollarded sycamore trees. Different strokes....enjoy your trip!

Of the three I've only been to Avignon. Went about 10 years ago. Not much there besides the bridge and popes palace. Was on the gritty side then.

If Arles is in the mix, I'd pick Arles over both Avignon and Aix-en-Provence. Yes, as the poster before me said, Avignon is gritty.