Most efficient stopover
 

looking at YYZ-CDG-BKK-DPS-PVG/PEK/HKG/NRT-YYZ
destination being DPS for saver award first class trip and not much good selection of flights on the return and AC trying to make the return mostly in economy
looking for most efficient stopover in terms of getting in and out of the airport and into the city, maybe with efficient train access or something that is of minimal pain-in the a**
maybe i am being ridiculous

HKG has an efficient train from the airport to downtown / Kowloon. You can even check your bags in at the train station, rather than the airport, when heading back to the airport on your return.

That would be nice here in North America!

CDG isn't bad, either. Frequent train service from T2 to central Paris. Takes about 45 minutes, costs IIRC 8€.

Depending on how long your stopover is, you can check in for your next flight (thus getting rid of your bags) or leave them at your hotel. A stopover that's so long you can't check in will be long enough for a hotel room.

I think it really comes down to which city you want to spend time in. Other than NRT to Tokyo, I don't think any of the airports is so absurdly far from the city as to (IMHO) override that.

I second this. HKG is great in their very efficient public transportation, and just how the city runs in general. They're very good at pushing masses of people from one place to another. It was truly an amazing sight.