I chose Collinsville because it's close to St. Louis, where I work, and because the cost of living here is reasonable. You can find a modest ranch here for only $100,000 or so. Since it's so close to the city, you'll find a good amount of job opportunities here. If you've just graduated college and are looking to start working right away, Collinsville is a good choice.
The public transit system here covers most of the downtown area. However, there isn't much in the way of stores so you will need your own vehicle anyways. If you're looking to visit a mall or try some new restaurants, you may need to check out a neighboring town for that.
Splash City Family Waterpark is a fun place to visit, especially in the summer. It's one of the best areas in Collinsville. The people here are very relaxed and welcoming and you'll be able to make new friends here easily.