BOS actually has fewer cancellations than you might expect. Because the airport is on the harbor, the airport is usually warmer than the rest of the region. So, when the Boston area gets snow, it's not uncommon for Logan to either have rain or substantially less snow than the rest of the area. Obviously, the airport can get substantial amounts of snow (esp with wetserly winds, which tend not to bring the same amount of moisture as southerlies, or with a monster storm regardless of wind direction.

While it's true that BOS has more weather-related delays in winter than in summer, it's rare that Logan is actually closed. Manchester is not at all a good alternative choice: MHT gets far, far more snow than does BOS each year, there are far fewer flights into MHT, and the drive from MHT to Boston can be awful in a snowstorm. Amtrak is no guarantee, either.

It's also obviously wise to arrive the afternoon or evening before any -Have-To-Be-There meetings.