I would suggest to check out
www.dlrpmagic.com and their discussion boards for more travel planning advice.
My last experiences at the resorts at DLP really made me decide not to stay in them any longer - with the exception of maybe Sequoia Lodge as it has had a recent refurbishment. But even then I don't think they give you value for the money you spend. It is lovely to be able to walk back to your hotel, but that's not worth the premium. With the non refurbished hotels I would be afraid to get a room that is falling apart (happened to me at SL before the refurbishment). And while Santa Fe is going through a refurbishment, that place is just depressing all around in my opinion.
There are a number of good neighbour hotels, but they would not be my first choice either as most of them are built in the middle of nowhere and unless you have a car you have to depend on a crowded bus (I saw amazing crowds trying to get on a bus to those hotels after Dreams on my recent trip, put any after Wishes chaos at WDW to shame).
You might want to check out the hotels at the Val d'Europe shopping centre, they are only one stop by RER from DLRP and those trains run on a regular schedule (and quite frequently depending on day of the week and time of day).
Depending on how much time you want to spend at DLP, staying in Paris and just taking the train out does make sense (even though I think it does take slightly longer than 35 minutes, I would calculate about 45 to 50 minutes) as you don't have to move hotel and you could alternate days in Paris with those at DLP.
If you are going over Christmas and trying to get EMH benefits by staying on property because of crowds: Certain DLP APs have EMH privileges. The Fantasy AP as well as the Dreams AP have them now. However, the Fantasy might be blocked out over the holidays. Christmas time in general is quite busy at DLP from all I hear. Even if those are more expensive than a normal ticket you might save money by staying offsite and getting those than paying the ridiculous DLP resort prices.
However, EMH aren't that exciting as only part of Fantasyland and Discoveryland are open. I have in the past been able to do all EMH attractions within one hour (and EMHs are 2 hours before park opening there).
One tip which I think is absolutely worth it for every visitor: Have a look at the Shareholders Club:
http://corporate.disneylandparis.com/shareholders/shareholders-club/index.xhtml If you buy 20 Euro Disney S.C.A. shares (currently at 3.54 € per share) you can become a member for free which gets you a 15% discount on tickets, merchandise and table service restaurants as well as entry to a private lounge at the entrance called Salon Mickey.
Hope this helps!!