Each of which are equally obnoxious and difficult to schedule appointments
I actually got my Nexus/GE at YUL, which (along with YYZ) I found much more difficult to schedule an appointment than JFK or EWR.
DW and two kids got or are scheduled in JFK (which was easier to schedule earlier in the year) and they were in and out in less than 10 minutes. Another son was lucky to get an appointment at US Customs House in lower Manhattan (someone must have cancelled) and they seemed a little obnoxious, but his card just came on Shabbos after I found something they would accept as proof of address (jfk didn't ask for anything).
I guess this issue is actually a plus for YYZ and YUL, as kids under 18 get Nexus/GE for free!