My experience with ArmA singleplayer in I and II was that they worked best with the base install. Newer patches tended to break certain scripted events in SP. Because of this, I'd expect the SP in ArmA 3 to work best with the patch it gets released with.
Single player barely shows off what ArmA is capable of anyways. Multiplayer has always where it's been at. It is one thing dealing with scripted events, another thing totally when dealing with the chaos of the battlefield. Never knowing quite where the enemy is at all times, taking risks that sometimes pay off handsomely or flop pathetically.