im almost positive YHZ has pre-clearance, so they’d clear US CBP there, and likely arrive in T1 (or potentially T2 if CR7 or smaller).

Id almost always opt for ORD over EWR, unless there is a huge advantage to EWR. I find he EWR experience awful, and that was before the airport was infected with the OTG ‘experience’. Much better food options at ORD. Connection time could be a factor though, particularly with kids (though you don’t mention ages). That said, the double-connection via EWR and SFO, as well as the 3 and a half hour connection would make me balk If traveling with the kids, especially if they are younger (though if it was just me, that part wouldn't bother me, assuming I have the time). And I just realized it’s a double connection anyway. 1 hour is probably less than ideal at ORD with kids, but still better than 3 and a half hours at EWR (with my kids, 4 and 1, I’ve done just under an hour and it works if everything’s on time, but prefer in the 1-2 hour range ideally - 3.5 and it’s a struggle to keep them entertained between flights). Both airports can be prone to weather, particularly thunderstorms in the summer months, but IME, EWR can be way worse - a bit of wind can cause ground delays really quickly. Plus, presumably there are alternates via SFO/LAX if for some reason you miss the ORD nonstop (though presumably true via EWR as well).

Aircraft has already been mentioned, but personally, I don’t notice the width difference too much. As already mentioned, 10-across can be seen as a positive when traveling in a party of 4, assuming you can snag a center section for the fam.