Dorval (YUL) is close to downtown and you can have a lovely evening in Montreal. Check Priceline's Express Deals or Expedia.ca for Downtown East of West. The airport area has nothing to recommend it and nowhere to go. If it's the middle of the winter, staying at the airport avoids the chance of a snowstorm blocking traffic.
As an aside, because YUL is so close to town, it can't expand and the government solved the expansion issue by building Mirabel on a distant farm field. After the airlines gave up on Mirabel because no one wanted to go there, it was used for movie sets for Tom Hanks and test flights for Bombardier.