The STI/SV guns are much better than the Paras - this is from a guy who has had multiples of both types. STI market guns specifically for CCW, without all the competition stuff that you don't want. Aside from the weight of the extra ammo, the STI guns are no different from a single-stack 1911 IMHO (about the same width, lighter unloaded weight)... if you are carrying the extra ammo anyway, what does it matter whether its in the gun or in a separate mag carrier ?
As for mags, my older STI mags ran like a top, but some newer ones I bought needed some tweaking... nothing major and still much better than Para mags. My current USPSA Limited pistol is in .40S&W, but the rounds have to be handloaded long to feed reliably in an STI. If you are going to CCW with it, I would suggest you go with .45ACP or 10mm Auto instead of .40, so you can run factory loads.