The centmin.sh script is designed specifically for that install: CentOS + Nginx, MySQL, PHP. If it works well for you and that's what you need, then definitely keep using it.

rayburst sets up a framework to allow for more customized installs. You can pick the various apps and services and the modularity of the build scripts/recipes handles the install of the configuration. Part of what takes place is figuring out the build dependencies (ex Rails depends on Ruby) which would otherwise have to be hardcoded in a bash script.