GCN did a test that concluded with a giant saddlebag coming out on top:
I bought the same saddlebag in the video and used it for wet weather commuting. (Loaded with jeans, shirt, button up, wallet, phone, keys, frozen burrito...) It made a good mudguard when I wasn't using an Ass-Saver.

Lately I've found a backpack to be more convenient for accessing stuff mid-ride. I toss the inner dry bag from the saddlebag into the backpack when it rains. Having the backpack at work is nice when I take trips to a grocery store or someplace else. I usually load up a fridge at work with sandwich components, so I don't need to transport food from home. When I do bring in leftovers, I just wrap the resealable containers in plastic wrap and they travel well. I have a filtered water pitcher at my desk and a small electric moka pot for coffee, so no drinks on the bike.

How do people handle pot luck events? That's been my biggest challenge.