score:5
You can stay in both airports. I have slept once in CDG due to a very early flight. It wouldn't be possible to get from Paris to the airport with public transport. No one will bother you. It's not a uncommon situation. The only annoyance that I had was around 2, I think, the cleaning personal cleans the floor, and the machine although not loud is noisy.
Regarding security: airports are probably between the safest places you have nowadays. Not that your things can't be stolen or something like that. That can always happen, but there is a lot of security and cameras which work at least as a dissuading factor.
It's important to know that you won't be allowed in the air side until you do the checkin and in many companies they will only allow you to check in a couple of hours before the flight. That means you can only stay on land side.
If you want yo know more about airports you should check this website: http://www.sleepinginairports.net/ Basically it gives you several tips and has reports by airport. You can easily find Barcelona and CDG airports there.
Upvote:0
Two days is a long time to stay at an airport (while doable). You are not constrained to the airport, find whatever cheap hotel you can find and enjoy your stay in Paris or the countryside -- the TGV stops at CDG. There's free wifi for your smartphone or paid work stations pretty much everywhere (Terminal 1, Terminals 2D, 2E, 2F and 2G.).
Upvote:2
There are plenty of hotels at CDG, including one right in the middle of Terminal 2 (on top of the train station, between halls ABCD on one side and EF on the other), and a bunch at Roissypole, from where you can reach Terminals 1 and 2 via the free inter-terminal light rail line, and Terminal 3 by foot.
There are more hotels a bit further away. I believe they provide shuttle services to/from the terminals, but you would probably need to budget more time as you would have to wait for the shuttle. Ask reception for timetables.
If your flight in not early in the morning, you may consider staying in central Paris. Hotels will be more expensive, but you'll have quite a few more things to do and enjoy.
Or you can even consider staying in Reims (30 mn away by TGV, though the TGV stops outside the city centre, and there are only 4 trains a day, with schedules that are not always very practical). Or Disneyland Paris (10 mn away by TGV, with the stations right in the middle of Terminal 2 on one side, and right at the gate of the resort on the other).