Hi M. - K. here again. Our current home was built by KB, and our new home will be built by Centex. KB is OK, but if you use them, I'd highly recommend hiring a professional inspector at critical building phases. KB construction can be a little sloppy. Also, if your neighborhood is in a hilly area, KB won't level the lots; they just build your house on a slope. Sounds like no big deal, but it leaves ugly foundations exposed and makes it hard for the kiddos to play in the back yard. Centex terraces the lots if necessary so that you have a flatter yard.
Differences I've seen with Centex in the neighborhood we're building in (Park at University Hills): Centex fully sods front and back yards in Bermuda (KB uses water hog St. Augustine and only sods part of the back yard). Centex installs a privacy fence. Centex installs "orange peel" textured ceilings; KB installs "popcorn" acoustic ceiling, probably to help cover shoddy construction. We found a huge arch in our bedroom ceiling while installing a border.
If you want lots of customization, use KB. Centex packages their interior color schemes (carpet, tile, countertop) and exteriors. KB lets you choose any combination you want and will even let you move walls / windows / doors in the house layout. Centex won't let you do that, even for a price. We've found Centex employees to be much more personable and responsive than KB, and overall we're more satisfied with Centex so far...time will tell.
Hope this insight helps.