FWIW, Carradice or oversized saddle bags have little appeal to me. They're well-made, but expensive and less versatile than a rack.
E.g. a Nelson + Bagman support = $170 or so. A decent rack + cheap panniers = $70. A Topeak rack + a waterproof stuff sack + straps = $55.
A Carradice saddle bag will also put the weight significantly higher than panniers, and a little bit higher than a trunk bag or a stuff sack on top of the rack.