I am planning a trip to Europe going through Boston from YYC for next year, part of a J return award trip.

Here is my skeleton itinerary going there:

YYC-xxx-BOS overnight
options
BOS-ZRH-xxx @21.45
BOS-IST-xxx @22.55
BOS-FRA-xxx @16.10
BOS-MUc-xxx @21.20

Here is the thing, need to connect getting to BOS and custom clearing. I want to see Boston on the way. Going via ORD is the best as I clear USA C in YYC and then just finding connection to BOS from there. Shortcoming is UA's lousy Business class. Via YYZ presents an issue with connection and customs time wise.

And then where should I stay to get the most of a layover. Hotel checkouts are early afternoon and I do not want to carry luggage around. Should I stay at the airport storing carry-on in the morning giving me lots of time to see the city, or should I go downtown late the night before and come back for a late departure. I do understand I have < 24 hrs to transfer through. Has someone done this and possibly can help me out. Once I figure that part out, I will ask for the best transportation means and suggestions how to maximize the 'visit', this would be my first time to Boston.