French Style and German Technology for BMW R1200GS
Here's a great example of how much of a difference can make a simple idea. Of course, you should probably have to be French to appreciate this for all it's worth. Or maybe a very keen wine-lover. Now, the hardcore adventure tourers could argue that they could fit a lot more wine bottles on their large BMW GS and still have plenty of storage occupied with all sorts of touring-specific gear.. and be right.
But you just don't take your girlfriend/ wife for a romantic evening with wine and candles while you both are covered in dust or mud. So maybe the other sidecase could store a nice picnic set, and even a small vase to hold the pretty flowers making things just perfect.
Now, one more important thing: just make sure you carry a tent, or have some lodging reservations, because wine and riding is not a good idea. And since you presumably like the person you're carrying as a passenger quite a lot, we believe there are many other better ideas than proposing in the hospital.