PCS to Scott AFB with the military. I own handguns with high capacity mags, and an AR15 with 30rd mags. I want to be able to CCW.

Do I move to some place in Illinois, or to St. Louis area?

I’ve been reading St. Louis is crime infested.

What’s the verdict? Where do I live affordable Amy and safe?

Living on base = registering firearms. No thanks.

No statewide AW or magazine bans in Illinois. Local bans are far away in the Chicago area.

If you change your residence to Illinois and get an Illinois DL, you will have to get an Illinois FOID card within a limited time (I think 60 days).
Illinois CCW does not have full reciprocity or recognition of any other state. There is in-vehicle carry for non-residents.

If your official residence and driver's license is from Texas, and you have a TX CCW, then you're from one of the few states that are allowed to apply for an Illinois CCL. Be advised that's a somewhat expensive proposition. Alternatively, if you changed your residence to Illinois you could apply as an IL resident. Illinois taxes are high and few want to change their legal residence to Illinois.

Either way you'll have to take an IL training class although you get partial time credit from being in the armed forces. If you happen to be traveling to Illinois before your move and have the time it might be worth finding a class ASAP so you could get the application process moving.
Parts of the city have become pretty bad, and it's spreading. Parts of the Illinois side are just as bad. Then again, If you drive the right direction from Scott you're in rural corn country, so it depends where you go and the environment you are looking for. I don't know if that is still the case but nearby Mascoutah used to be popular and had good schools if you have kids.

No kids, no family.

My DL and CCW are for SC.

I’m thinking I’ll retain my SC DL/Permit and live in Missouri. Only travel to Illinois will be for work. In vehicle carry is enough for me.

Somewhere on the south side of St Louis would be easiest on the commute I think, the I-255/270 route from the south isn't bad. Traffic on Hwy40/I-64 and I-70 through downtown is usually difficult, and 270 around to the north side is a lot further drive.

MO recognizes all carry permits/licenses so you're GTG on carry in Missouri. Can't carry on public transportation.

Mascoutah, Shilo, and O'Fallon are all generally pretty good. Parts of Belleville are OK, but some aren't any more.. All are within 15 minutes of the base, although rush hour can change that.

If you go the living in MO route. Look in the area around 55 and 255. With that you can hit 255 up to Illinois 15 and cut in the back way to base and save a ton of time. It us rare that that route has any issues.

Welcome to the area, I’m retired USAF, will will be retiring this summer.

The O’Fallon and Troy areas are good if you care to live in Illinoistan.

** The on base registration has been rescinded as of 1 Jan 2018