re: Going to Paris and London-need help

With only 3 days, I'd say do all of them in one city. Its hard for me to tell someone that has never been to either to only do one because seeing the difference is worth quite a bit, but ultimately I think 3 days is really just not that much time and 6 days between the two would be very very busy.

I'd recommend all the time in Paris. You will then have plenty of time to do a relaxing day trip to Versailles, and you could potentially do a day trip elsewhere though I wouldn't plan that until you got there and felt like you had an extra day.

Its so much more enjoyable to have that extra time to spend in those cities then busting it to get from A to Z so you see everything. Especially in Paris and London.