I lived in Marietta about 3 years ago and now live in the city of Atlanta - one thing besides what every one else has said is that the taxes are much lower in Cobb county! We live just (and I mean just) over the county line from Cobb County and you will have to pay city + county taxes if you were to choose that route versus directly in Cobb county.
Another thing is that even though he is getting a job in Marietta, that doesn't mean you have to live directly in Marietta. I don't know what your budget would be, but some Marietta addresses and areas can be a bit pricey for homes. However, my husband and I have considered moving to one of those areas because of the school districts. You can very easily live in Smyrna and some Atlanta addresses and still be pretty close to Marietta.