Hyundai Sonata vs Toyota Camry used under $18,000 CAD. which is actually worth buying?

Buy the Camry. This is not close.

Owner data on the Hyundai Sonata from 2011 to 2019 shows widespread reports of engine failure from the Theta II GDI engine, specifically premature wear causing metal debris in the oil, bearing failures, and catastrophic engine seizure. Hyundai extended warranties and ran recalls, but many cars in the used market are past the coverage window. A 2015 to 2018 Sonata at 130,000 km that looks clean on the surface can fail without warning. A used engine replacement costs $4,000 to $6,000 CAD.

The Toyota Camry in the same year range and budget carries none of that risk. Owner sentiment is overwhelmingly positive for long-term reliability and low cost of operation. The 2.5L four-cylinder and 3.5L V6 are both proven engines that routinely reach 300,000 km. The only thing to verify on the four-cylinder 2012 to 2017 is oil consumption: do a consumption test over 1,000 km before buying.

The Honda Accord is the only other car worth considering in this segment. The 2016 to 2018 Accord shares the Camry's bulletproof reputation and owners describe it as equally dependable over long-term ownership.

If you want to keep a car for 5 to 7 years, the Sonata introduces a risk of a repair that exceeds the car's value. The Camry does not. Spend $1,000 more to get a Camry if needed. It is worth it.