The first question came up in a thread recently, when I said the idea of all that side area put me off them. I hate side winds (and head winds, come to that) as it is. The answer from those who've used them was that they have less effect than panniers (which was no good to me cos I was comparing them, mentally, with saddle bags, but might be relevant to you – though the capacity seems more like a large saddlebag than a pannier, I think).