Thanks for reading, Cory! From my understanding, some of the performance enhancements came from the reduction of the system font to solely one. Segoe UI was also optimized for Vista’s default ClearType rendering environment. I’m sure there were other reasons as well, but I can’t quite recall them right now.
For more general knowledge on this typeface today, check out Windows Dev Center — https://msdn.microsoft.com/en-us/library/windows/desktop/dn742483(v=vs.85).aspx