In the past we've used the RER and Metro but this time there will be 4 or 8 of us depending on airline arrivals. What do you suggest for the trip?

And why not the RER since it is a direct line to St. Michel at the foot of the Boul' Mich'?

At what intervals will you be arriving? Will all of you be traveling together?

someone will soon be recommending some shuttle service that may well be cheaper than 4 or 8 tickets and more convenient - terminal to hotel. RER, at least if landing at Terminal 1, most trans-Atlantic flights, involves taking a 'navette' shuttle bus from terminal 1 to the RER station, navigating the ticket line and then wedging baggage thru turnstiles then again thru turnstiles perhaps to get out and you're still not at your hotel. I always take the RER, as a single traveler, but it's not a piece of cake. And not US State Dept's warnings on bag thieves on these trains.

Both groups, 4 in each, are arriving on AA about 1/2 hour apart, ours from DFW arriving 10:00A the other from JFK later.

Two taxis. 10€ each.

I agree with G.

The two taxis might be 15E pp, w/luggage.