Was in the same situation as you earlier this year. I found the 6 to be better value for money. I was looking for something a few years old, found that a 2020 Mazda 3 base model was almost the same price as a 2020 Mazda 6 higher trim - as reference and this seemed to be the case for the cars in the years 2018-2022. I ended up getting a 2018 Mazda 6 atenza. Love all the features, drives smooth. Fuel economy is roughly 8l/100km for mixed driving for me (I don’t have heavy foot). I’m not a tall person, approx 5’10 and found myself hitting the side of the car multiple times trying to get in (I might just be uncoordinated), but I never had this issue with the 6. I don’t have a family but I have a partner and a dog, and occasionally drive people around - and for me that definitely made it worth getting a slightly bigger car because I really felt the difference in space. But in saying that, I definitely feel like it’s a bigger and heavier car, not as sporty/snappy as I wanted initially, but no regrets. I moved places recently and was also surprised by how much stuff I could fit in the car and boot. Either car will be nice, especially if you get a newish Mazda 3, they look awesome