First time travelers to both places. Where are good central locations in each city to look for hotels where it's convenient to do sightseeing, walk to restaurants/bars?
Hotel La Cathedral, near the main cathedral is a good hotel, central to the city. Lots of walking from there.
In Paris, the Latin Quarter and the Marais.
How long in each city? If a week or close to it, an apt. can be cheaper, bigger, and better.
Do you have RS guide books for those two locations? If so, good. If not, you should get both of them as they are full of information you can use while visiting both.