If you are looking to get any sleep at all, Isaac's Hostel is not the place to stay! The place was insanely loud, when I walked in the staff said they were messing with a cell phone they had found, and it felt very overcrowded. Definitely the place for people who are only looking for an unclean and loud party.
Le Montclair Montmarte was perfect for my stay in Paris! It was conveniently located near public transportation, staff were very helpful, and our room had a great view. I would definitely come back and have already recommended this hostel to friends!