In general, SiteBuilder 2.1.2 for Linux and SiteBuilder 2.0.5 for Windows is the same. They has the same main features.
There are some differences:
1. SiteBuilder for Windows publish trial site possibility. (the main difference)
2. Windows version has read-only 'Reseller' field 'General Properties' tab of Site Management.
3. Widows version has 'Site Host Name' field.
I think there are some more but they are insignificant.