The Montreal Jazz Festival announced its winter series August 16. Two of its concerts overlapped the Ottawa Jazz Festival's winter offerings, and there were several others which will also reach Ottawa or Gatineau by other means (Michael Kaeshammer, Al Di Meola). (However, Sophie Milman seems to be Montreal-only so far.)
But the Montreal tickets for the SF Jazz Collective were substantially less expensive: $37.89 in Montreal ($31.50+ taxes/fees), against $57.50/$50.50 + $5 in Ottawa.
Tickets for the Ari Hoenig Quartet were more expensive: $34.47 in Montreal ($28.50 + taxes/fees) versus $22 + optional fees in Ottawa.
Of note, the Ottawa Jazz Festival is offering $7 off on SF Jazz Collective tickets bought before Sept. 12, and the collective will be appearing in a theatre with reserved seating in Ottawa, as opposed to general admission in Montreal. But in Montreal, you'll be able to have a beer or drink with the show, if you like that. One might also expect a slightly different show, given the different environment (think NAC Studio versus 4th Stage).
It's not likely to be worth your while to save a few dollars by rushing to Montreal (unless you really like beer with your music!) but the differing price structures involved are interesting.