Marais vs 7th arr

First time in Paris march 24 to 28th

Have been recommended to stay in Marais as it is near cafes, restaurants and bars.

Unsure whether we should stay in 7th due to our first time in Paris.

We want to spend about €650 for the 4 nights.

Any thoughts and suggestions are welcome. Want to be near some nightlife and some cool spots throughout the day. We love to walk but wouldn't mind also being near access to public transport so we can go and see the sights if too far on foot.

We are 27 and 30 years old.

Thanks!