Use the search thread at the top and you will read some of the past threads in the last couple months on these cities.

Personally,I would do Marrakesh and Essaouira as the two represent two different types of Morocco to me.Our family spent three days over Christmas(along with another week an a half driving through Morocco) in Essaouira this last December and loved this gem on the ocean!It is the type of place that you can shop(with better prices than Marrakesh);has reasonable hammans,also has fabulous restaurants and cute riads.
It has an unbelievable coastal area for watching the fishing boats and fish market,a beautiful square for great people watching and a coastal drive to see the infamous goats in the trees or just taking a day on a gorgeous beach.(If you decide to go to Essaourira,let me know as I now know where the "underground" liquor store is for expats-too funny as I asked a French woman in the big local grocery store chain about it and she graciously drove me to it.LOL)

Fes was just too touristy for our family and quite honestly a letdown.Marrakesh and the Jemma square is amazing-be sure to spend an evening eating at the various stalls!(The soup stall and the calamari stalls are yummy along with the fresh squeezed orange juice!)Between the two,the whole atmosphere of Marrakesh is so much better than Fes.

Thank you so much for your help! Essaouira sounds amazing. I appreciate your advice! Do you have any advice on the best way to get to Essaouira from Marrakesh? Bus or car? We have 7 days total in Morocco. Would you recommend splitting our time half and half between the two places?

Funny, I had the opposite reaction to dutyfree. I thought Marrakesh was more touristy than Fes. And while I really enjoyed Essaouira, it isn't very "Moroccan". Click on my name for my TR.