Picking a base in Paris really comes down to a trade-off between being steps from the postcard sights and getting a more local, everyday feel of the city. Stay in the 7th arrondissement on the Left Bank and you'll be a short walk from the Eiffel Tower, the Seine, and the Musée d'Orsay's Impressionist collection — but you'll pay for that location, and rooms tend to be smaller.
Move a bit further out to the 11th or 12th arrondissement and the rates drop noticeably, while you trade very little in terms of access — both are well connected by metro. These neighbourhoods also tend to have a better everyday food scene: bakeries, small markets and bistros that serve locals rather than tour groups. If you want help weighing cost against how much time you'll spend on transit, our hotel booking guide walks through the trade-offs in more detail.