All I know about osprey is that my two packs from them are very nice (but larger than what you are looking for) and that they have one of the best warranties in the business.
But with all packs, an inch here or there can make all the difference, figure out your likely total weight and do your best to try them on with some ballast. Or if you can, get both and run them, you won't get all your money back on the re-sell, but consider it a learning cost and it won't be that big of a deal. I know a lot of "really good" packs just don't fit everyone. As for the shoulder strap thing, that is a factor with packs of that size, and has a lot to do with how high you wear them, your body type and activity. I'd bet a lot of reviewers of the BD were scrambling, so hands up high a lot, where the osprey reviewers were just day-walking, and it was less noticeable. I don't really think you'll go wrong either way, just think about the secondary features, the BD is a tougher scramble pack, so heavier, and the osprey has cargo compression (a little at least). Each is going to have a different value, depending on your uses.
