Use Business. Ultimate is just Business with a bunch of stuff that you don't care about thrown in like extra eye-candy, games etc..
Link
My system runs archicad noticeably faster in Vista x64 than it did in XP x64(about 10%-15% difference), and since SP1 Vista has been a lot better of a platform. I don't regret upgrading yet.
Josh Osborne - Central Innovation
HP Zbook Studio G4 - Windows 10 Pro, Intel i7 7820HQ, 32Gb RAM, Quadro M1200