IMHO you get the best deal by buying this gold edition disk version that contains the sh4 game plus the ubm v1.5 ad-on and you never need to worry about reinstalls or activation issues again.
plus by buying thru subsim they make a donation that helps fund this website so you pay a little more to get a disk in your hands and you own the game forever plus you help support this website.
http://www.amazon.com/dp/B001BBS8B0?...m%2Fstore.html