OP, welcome to FT!
My first question would be where are you flying to? AC serves a lot more US destinations from YYZ than DL does. If you're already doing a lot of YYZ-ORD/EWR-xxx, maybe it's a wash to do YYZ-MSP/ATL-xxx or whatever. But I would say there's no way the loyalty program is worth adding a lot of inconvenience to your travels.
Another point for consideration: I fly DL a decent amount - never quite enough to achieve status. A while back, I had racked up 100K or so SkyMiles, yet I could never seem to use them. When I would find availability, it would often be for silly things like 200K points for YYC-MSY round trip or something like that. It's a lot like Market Fare on Aeroplan if you're trying to redeem on DL metal. I think there are some decent partner awards still available on fixed mileage if it happens to work out for you (I got some okay, but not great, value on VA domestic flights in J in the end), but I wouldn't expect the reward redemption aspect of the program to be much more favourable than Aeroplan.
I generally quite like DL though. One drawback is that they recently joined AA in excluding Canada, Mexico, and maybe Caribbean (I haven't checked) from being "international" destinations that qualify for lounge access. So even if flying J on, say, YYZ-ATL-GDL, you'll need a credit card to grant you lounge access (although Amex Platinum will do). But overall I find the crews to be pleasant, planes to be in pretty good shape, OTP good (padded block times), and customer service generally quite good.