The one thing that is a little sticky is that you can't get across the border if you have had a DUI within so many years. An issue for some of my dad's hunting buddies.
The US side coming back was always a bigger pain in the neck. Part of that is because of the way Border Patrol rotates their agents. You could always tell the ones that had recently rotated from the Mexican border because they were twitchy and kept a hand on their holster at all times. I'm sure it's a hard habit to break, but not really appropriate at a backwater crossing in Northern Maine where 95% of the traffic is log trucks and local Canadians coming over to fill up their gas tanks or pick up things they've ordered online.
The only two times I've been aggressively grilled including accusations of smuggling and personal questions that were intrusive were coming back into Canada.
Even when I only had a green card, most of the time the US CBP just said "welcome home" and waved me on.
I don't think it was the difference between being a visitor (to the USA) vs a resident (in Canada), because the couple of times I went abroad while I was a resident in the USA were very similar.
Straightforward business trips for both countries for me, but Canada is a little more casual than average, but otherwise uninteresting. The officials smile, ask a straightforward question ("where are you staying?"), and stamp the passport ("enjoy your stay in Canada").
In the US, I feel like I'm being interrogated. "You don't look like a software developer" "who is paying for this trip?" and lots of scowling.
That would be considered unacceptable and unprofessional at U.S. border control.
We had six people and a ton of luggage and they seemed to be seriously considering searching all our bags just because of Texas IDs. :|