This is kind of a loaded question, because different places are good for different things and are culturally (within and without the mongering community) different as well. On top of that, people have very specific preferences about things outside of mongering, like climate, presence or absence of beaches, language issues, ease and length of flights, etc. etc. Also, while some people might frequent one place more often very few who travel regulalry will limit themselves to one location. So, bearing that in mind, my favorites are as follows, in no particular order:
1) Medellin, Colombia. Great climate, modern conveniences, an easily accesible network of gorgeous women
2) Lima, Peru. Super interesting place to visit, world class cuisine, down to earth girls, not out to gouge gringos every second of the day
3) Angeles City and Subic, the Philippines. GFE capital of the world, very cheap to monger, stay and eat, super friendly, English speaking
4) Kuala Lumpur, Malaysia. Exotic, modern, cheap. Interesting venues and great food. I love the vibe here. The mongering scene is layered here.
5) Havana, Cuba. The city has issues with modern conveniences, but has charm and music everywhere. The girls are hot, cheap, and available all over the city in any kind of venue.
Many other places, some of them fun, but not favorites. The only ones I wouldn't do again for mongering purposes are Mexico and Paraguay.
How do they compare to Montreal? They blow Montreal away in pretty much every sense of the mongering experience. Also, every single one of them delivers far greater value for the money, by a significant and sometimes ridiculous margin. It's not even close, really. The downside of course is that you have to travel. Traveling is great, and I encourage it highly, but it can affect someone who wants to be on a regular schedule.