Hi Ben, two of us arrive at CDG on 28 June, leaving for Lorient on 4 July. What's your opinion on best option for a Metro ticket/RER (we want to visit Versailles for one of the days). The rest of the days we'll be travelling from the 15th precinct into central Paris. A bit confused with the Navigo options etc. Cheers Richard
For the period of Wed June 28 till Sunday July 2, I'd still recommend a Navigo Découverte week pass with default coverage of 1-5 zones. This will cover you from CDG to Paris, your Paris - Versailles trip (11.45€ one-way + 8.10€ return = 19.55€) and daily trips from 15th district to anywhere in Paris/Ile-de-France. Total cost per person is 35€ (30€ for week coverage and 5€ for card itself).
I generally recommend unlimited passes when the price difference vs. stored-value isn't too large because it removes the internal mental/emotional noise of "maximizing this transit ticket". Without this concern we get to wander/explore Paris with more focus on simply enjoying our time, rather than worrying about making mistakes by taking the wrong bus or Metro/RER. Having an unlimited pass almost encourages us to get lost in the city and discover some hidden things we didn't expect. Btw, I recommend taking random buses around the city when you aren't pressed for time. It allows you to see the city more and get off anytime something catches your eye. Traveling by underground Metro tunnels is great for speed but not great for exploring.
For the Monday/Tuesday this is more tricky. Perhaps just single-use, paper Metro tickets or wandering around on foot. But if you plan to take 4 or more one-way rides during a single day on Monday or Tuesday, put a 1-2 zone Navigo day pass onto your Navigo Découverte which is 8.45€, so basically the same cost as 4 one way Metro/Bus rides. You can do this at automated ticket machines at Metro/RER stations or at Metro/RER ticket windows.
The Navigo Easy I'm hesitant to recommend because you can't put RER tickets on it. i.e. you can't use it for RER B from CDG Airport (you'd need to use Roissybus & add that specific ticket) nor Transilien trains/RER C to Versailles (you'd need to take either Metro + bus, or bus + bus, neither of which are simple/straightforward itineraries). And the rest of your trip you might be wondering how many Metro/bus rides you have left on your pass. So, a bit distracting / more complicated.
Anyhow, have a great trip.