You said there will be 50/50 on/off roading...
But...I think you have to decide how heavy offroading you have in mind.
If you will do only gravel roads, better trails... than you can choose BMW or 990.
If you will do heavy offroading, rocks, mud... than you should consider Tenere, because its lighter. Maybe on paper its not much lighter, but on terrain 15-20 kilograms makes a big difference.
I had 990, and sold it (also) because of that. It had great performance, but could not use it much on hard trails.
With Tenere I feel much lighter and confortable, the bike is a whole lot more agile.
Think about that too, when making decisions.