I've got a DB cover for my Adv 1150 - it fits perfectly even with the panniers on, it will go over the whole lot. After 3 years it is getting a couple of places where it is wearing thin - like you my bike resides out all th etime, nowhere to put it.
I would get another one - this one will last another year or two before the sunlight causes the material to go brittle, then the holes will appear rapidly I would think. For the price,it was a good buy.
I canot say about the Oxford one, I haven't seen it.