Just get the car that you "feel" connected or really want to own. No need to think so hard about the differences. Go test drive both cars, all the variants, be thick face enough to test drive a few times and longer distances. Request to drive on longer routes, preferably those that you use the most like those to and fro workplace. IF they don't allow on that day itself, schedule a time where they can make arrangement to block longer time for you. If they still don't allow. get another sales adviser or another dealer.
I test drive for more than 70km totally more than 1 hour on the Mazda3 and dealer and sales adviser entertained my request happily. The sales adviser also let me go up to highway (toll bayar sendiri la of course), drive above speed limit almost the whole stretch. The SA some more mention don't know why people don't dare test drive further and harder, so i must be a rare one. Just that another sales advisor with a potential customer kind of angry as they waited longer than expected.
Engine performance wise is pretty much similar for normal driving. The Civic might have better response as it is a more powerful turbocharged engine after all. However, the Skyactiv engine is no slouch either and can rev up quite easily. The behavior is also different due to the type of transmission used. So again, go test drive and "feel" which you prefer.
Bring your family along if that's a concern to you. If not, better don't as will be more opinions and viewpoints that confuses you. If you're an active person that does sports, bring along your sports equipment and see whether you can secure/fit into the cabin/boot properly. Big is nice but doesn't always mean best. How likely are you to fit the boot to the brim in your current car's ownership. Hardly or never right?
Road noise is a bit subjective. Some can be higher pitched, some lower pitched. Tyres also play a part. Mazda comes with a set of performance tyres from factory. These tyres' is noisier in nature as the compounds are harder for better grip and lesser sidewall flexing. The Civic on the other hand comes with normal tyres. Hence will be more cosseting.
The mazda definitely losses out in interior space, but I ferry my family around with it including a baby in a baby chair and no one complains about being squeezy. If you're close or above 6 feet, only than the difference can be greatly felt. On a side note, my baby likes it when I corner hard on the mazda

IF still really can't decide, just go for the Civic. Even halfway through you hate the car, you can ditch it easily as the resale market for it is good.
This post has been edited by wkc5657: Jul 25 2016, 03:34 PM