I will provide a 'template' and you can fill in the blanks with your personal opinions.
Also, flea market is "Marché des puces en plein air" and mall is "Galerie Marchande"
Je préfère faire les courses dans _________ pour plusieurs des raisons. Le __________ a _____________ et _______________. D'autre part, le _____________ est ______________, et je n'aime pas ce characteristique.
English Translation:
I prefer shopping in ____________ (your choice) for many reasons. The ____________ (what you chose earlier) is _____________ (something you like about it) and __________________ (how you feel about it). On the other hand, the _______________ (the one you didn't chose) is _______________ (something you dislike about it) and I do not like this trait.