if you are living in US, most lawyers will advise (in fact insist) on AOS. It really isn't a TN matter. All persons in legal US status are advised the same way when choosing.
I chose AOS. This is because that is what gets you (and your depandants) work authorization faster, and off TN. Also, CP is subject to the mood of the consular officer that day, and a slight misstep on your part-- with no lawyer and no appeal -- gets you booted (thus the insistence that lawyers to remain in control of AOS). And consulates have their own backed-up timeframes, and you need rto do a LOT of things in a couple of weeks while in Montreal, doctors, rcmp, etc. Highly stressful. There was a time, when I-140 was considered immig intent, that CP was preferred because it was proof-positive that you were going to have to leave the country to get GC, but that worry was erased long ago.
Just for completeness. You can always indicate CP on your I-140, and then change to AOS later. Doing the reverse however is difficult.