I want to know what's your take on the reliability of a manual transmission mazda 6 from the mid to late 2000's when compared to camrys and accords of that same time period.
Those were decent cars, if you can get it for a good price then go for it. They also had good manual transmissions and four cylinder engines. One thing to keep in mind is back then Mazda didn't make their own six cylinder engines, all of their six cylinder engines were supplied by Ford. That engine had a timing chain driven water pump so you want to make sure that you maintain it properly because if either the timing chain or water pump fail it could be catastrophic.
With lower mileage and proper maintenance they can be decent cars, especially with a manual.
You can look here for problematic years and common issues: https://www.carcomplaints.com/Mazda/MAZDA6/
Back then Mazda was interconnected with so many companies so it had many engines shared with Ford and design elements shared with Volvo.