I just returned from hosting a trip to London and Paris for university
students and teachers. I agree with Ken that the D'Orsay would be my first
choice, but the Louvre is one of those tourist attractions that everyone
seems compelled to see. It's sort of like visiting Arizona and being
obligated to see the Grand Canyon.
The folks from my group who went to the Louvre had a great time and enjoyed
the collection. Most complained, however, that the major works they wanted
to view up close were in crowded galleries. Be prepared for that.
The D'Orsay is an encyclopedic collection, just not as large as the Louvre's
collection. The galleries are generally easier to navigate and the place is
usually less crowded than the Louvre.
Regardless of which museums you decide to visit, if you are spending at
least one full day in museums, I recommend buying the Museum Pass.
http://www.ratp.fr/ParisVisite/Eng/Actuas/m&m/musetmonument.htm These are
available at Tobacco Shops, the tourist booths, and at the museums and
monuments themselves. Unless you go to more than two museums or monuments in
one day, you won't save much money with the pass, but you will save your
limited museum visit time. The pass allows you to enter the museums without
waiting in line. In museums such as the Louvre the line to enter can
sometimes stretch for more than a block. Being able to walk past that line
might be the difference in getting to see one museum or two in a single day.
You'll find many Parisian cafes and bistros with sidewalk tables. Be sure to
try the crepes that are available throughout the city at the walk-up