The main differences are;
* Addition of a firing pin block in the P232
* Slide serrations evolved, there are three styles, call them "Many", "Fewer" and "Perpendicular"
* Sights, go from two dot to three dot
* Standard grip panels changed but are interchangable.
* The P230 came in multiple calibers, .380, .32 and 9X18 Ultra. The P230 pictured is a .32acp.
This picture shows two of the three slide serration iterations. I don't own the newest model which has the seration at a more perpendicular angle, less slant.
Note the four types of grip that were at one time available;
New style plastic
Hogue (standard on some models)
Old style plastic
Nill (never standard to my knowedge but sold by Sig)
Here's a picture, not mine, of the newest serrations.