I've never shot an over and under rifle (though do I love my o/u shotguns) as I must say I'm quite partial to side by sides. I did see a Beretta 689 when in New York last month. Aside from the fact that the rifle was in a format that was completely new to me, I must say it seemed very well made and I think I would have enjoyed shooting it.
Traditional dangerous game hunters have favored side by sides as compared to o/u's thinking that they can be reloaded faster as the gun does not need to be opened as wide in order to insert new bullets. That said, in terms of shooting a gun for accuracy, when was the last time you saw anything but an over and under in sporting clays or Olympic competition? Both designs have merit, and I'm sure the 689 has its advantages, but you won't see many when wandering the plains of Africa.