Cirencester and Swindon are very different towns.
My parents live in Cirnecester and we live in Swindon.
Cirencester is wealthy, nice, lots of boutique style shops, generally quite up market in everything. Schools are (mostly) good - avoid Watermoor. Secondary school as seriously excellent. It is a lovely, pretty town.
downsides - it is very white middle class and can be snobby. My dh is dutch, and found people were less welcoming in Cirencester than Swindon (a lot less - very polite, but distant - you aren't one of us)
There is also less to do. Most social life revolves around restaurant type activities. It is also smaller.
Swindon is a much larger more working class town. It has a rubbish town centre, but outside of that it has lots going on. There is loads to do, leisure centres, bowling, theatre, kids play areas, cinemas, etc etc etc. I have found it to be very welcoming and Dh says that here he is accepted as just abother person. As Swindon was built they have built in green spaces, play areas and cylce paths, I can get to most places in Swindon on a bike, with veyr little along actual roads. Parts of swindon can be run down and grotty, don't live in Pinehurst, Penhill or The Parks. North Swindon is good, but there is pressure on school places, as they didn't build new schools alongside new houses. Primary schools in Swindon tend to be good. (unless in one of the areas above)
Secondary schools in Swindon aren't great, but there are schools you can travel to that are good.
Loads going on for families, mums and toddler groups etc.
Commuting is easy and not far.
Feel free to pm me, and when you get here, let's meet for coffee (lorney too?)