I think that you'll find that there are customs restrictions on how long a US registered airplane can remain in Canada. That said, I think that if you pay the import duty on it, the customs people might relax.
Remind yourself that the " " Canadian bureaucracy offers some ownership options for airplane cost saving that the US does not. each is different, and I have no problem with the Canadian system, having owned more than one airplane in Canada since 1987.
As for low cost Seneca, vs more expensive 172 - yeah, I see that! Depending upon the year of the Seneca, it may be very poorly supported compared to the 172. Literally, when I spoke to Piper years back about a client's Seneca I, and the absence of a required primary structure part, the response was that they would not support the airplane with this part - period. The part had to be custom made and approved for the return to service. With legacy airplanes, you'd better do your homework! I've been consulting with a customer recently maintaining a light twin. For want of a very unavailable nose gear actuator, the plane is grounded indefinitely, and with a very large bill (probably 5% of the value of the whole plane) for one, if/when it becomes available. Select the most common legacy airplane you can find - there are way more parts out there to keep it going!
If you really feel that you must have an N registered plane, well, the border is only a few hours drive, best to keep it on the other side!