You did not tell us:
your budget, how many people traveling, plans to go out of town (sleep outside Paris), preferences or ability to move around
If you are staying for an entire month, and will not be spending many nights outside of Paris (use Paris as a base for other travel), then I think an apartment is the way to go. I have stayed for 3 weeks before (usually stay for a few days in hotels) and an apartment not only saves money but also allows for more space and flexibility.
If money is no object and you just want to accumulate points then there are tons of "chain hotels" that you could use.
Since you bought a ticket on XL, I assume budget is a concern so unless you find a very cheap hotel deal, I think one month stay will work better in an apartment.
Mercure (part of Accor) has several nice and nicely priced hotels in Paris and you will be amazed how prices drop as you get closer to the date. Maybe even call them and see what is the price for one month. Rooms tend to be smallish.
Citadiines is nice but expensive. small studio with kitchenette can run easily 200 euros a day.
I have used this company several times. I prefer the 6th arr but it is because it has everything I want day and night. They have apartments all over. Email them and you will get a better monthly deal.
http://www.parisrentaparts.com/PBCPP...ERM&varLang=US
Regarding where to stay, metro stop is never far away; at most you need to connect Metros. I prefer the 1-8 arr but that is me. I have been coming to Paris since I was a child and that was my parent's favorite area. All areas are safe but the farther you get from these areas it becomes "less desirable" and "more edgy and trendy" - whatever that means and whatever that is worth.
You could also consider staying totally out of town. Versailles or some other little town will be a lot cheaper but it means a train ride every day into Paris. If your heart is staying in Paris for one month I would NOT stay outside the city peripherique
You should read the forums; lots of information on where to stay, what to see and about apartments. use the search function.
One of my "bucket list" items is 3 months in Paris. I have never had the time to do that but will ----- when I have the time.
best of luck
PM me if you have specific questions I can help you.