The Sun Also Rises and A Moveable Feast actually share many similarities, despite the fact that one is meant to be fiction and the other a memoir.

• both take place in Paris of the 1920s
• the primary action of the majority of the main characters/people in each book is drinking coffee and drinking alcohol. They do a lot of restaurant, bar, and café hopping
• in both books many of the conversations revolve around sex or affairs
• the people in each book appear to be a bit lost  (existentially) or in search of themselves
• the groups of friends in each book are largely made up of expatriates

One key difference between the two is the age of the author at the time of writing the books. The Sun Also Rises was Hemingway's first published novel, and he wrote this while he was in his mid-twenties and not far-removed from living in Paris. He wrote A Moveable Feast towards the end of his life and it was actually published in 1964, after he had already died. Each of the stories he shares in Feast are based on memories of events that occurred decades earlier, and many have argued that the memories were still crafted to elicit certain images of his "friends," not that they were necessarily true. So, in a way, Feast has been considered a sort of fiction because we have to wonder what Hemingway might have changed in order to portray some episodes in a way that were most flattering to him.