By doing Consular, he enters with greencard in hand, no adjustment, potentially no removal of conditions, just keep calm, carry on and as long as your marriage is strong, he can apply for citizenship after 3 years. If you're married 2 years plus a day or longer when he crosses the border, he will get a 10 year greencard. Consular has a certain level of "cleanliness" associated with it when it comes to packing up, moving and starting life.
Adjusting means he can't travel back and forth to Canada unless he has advanced parole, which is a real crapshoot much of the time, but is really questionable with this administration. He can't work until he has work authorization. The process will ultimately cost a lot more because of all of the steps and if you spend any time on here, many people are stuck in removal of conditions proceedings for forever. Many apply for citizenship and request a combo interview because it takes so long.
Canada is hardly overseas and has a different agreement with the US when it comes to visas. Canadians are some of the most notorious bunches for overstaying because it's visa on arrival, here's your B1 stamp, ttyl. CBP typically don't check; it's left up to the person. Unless, of course, CBP start to see a pattern.
There are rules to retain provincial social benefits in Canada, as I'd mentioned, residency and presence being part of that. The Canadian federal government deems you a non-resident if you don't have significant residential ties and you spend more than 183 days away. So, while CBP may stamp a 6mo entry into the passport, it doesn't mean there aren't consequences "back home" to deal with.