I think it's clearly mentioned in post 1 that the OP was driven by cost and redemption availability with 3 people, so that adds a lot of friction to the process. And the Trafalgar won't be on their schedule! Massy HGI is indeed next to the RER B line station, but it's essentially a hotel for Orly airport, so the lengthy commute will figure. It won't take an hour to get to Châtelet, but most tourist spots are going to involve a second metro trip from there. But for the fact that there is another HGI for Orly, I'm quite sure that HGI Massy would be have been called Orly HGI. it's a bit odd really, the metro in central Paris has stations very close together so the suggested HGI in la Villette could lead to 45 minute long metro trips to say the Eiffel Tower, but la Villette is central Paris and the city's bars and restaurants are on your doorstep. That's not the case for Massy, which is a somewhat grim part of the banlieu (suburbs). That said, hotel prices in Paris can be as crazy as all the major European cities, so there will be times where HGI Massy will make sense, or at least be affordable, so it's a valid suggestion in that context. There are more affordable Hamptons around London's suburbs which could do a similar role (e.g. Park Royal, also next to a tube station).