Both those places are extremely Beautiful and would be a great place if you are Rich...........
Having said that and also as one who has hosted more than one International Conference, I also realize that there are certain factors that make a conference successful rather than a dream holiday.
Expense being the main topic as if it gets to pricey some may not attend.
Ease and expense of Transportation to/from the site
Accomodations and meeting rooms
Items of interest while there
All those are the main items considered when hosting a larger conference.
The Punchline is that La$ Vega$ has it all. In fact the NBAA will be here next month which says something..
So if your on Holiday, yes head to Canada, if your going to host a large conference, consider Las Vegas.........
Ned you have been here, how soon you forget.......Your Beer is still cold.