Bill's Bag is a decent choice
I've got a LARGE Bill's bag (3.8 cu ft) I've had for 20 years and a smaller one (2.2 cu ft) that I've had maybe a dozen years or so. When I was strictly a kayaker, the big bag was the one and only thing I'd bring on trips. I bought the smaller one for a GC trip, and I prefer it now. If I need to pack more, I bring a Tuff Sack of whatever size works. I have a Seattle Sports small roll-top dry bag with shoulder straps, and it's been good, too.
The stitching on the strap of the big Bill's Bag ripped on a GC trip last year. It's still dry, but you can only use one of the two straps. I'm kind of retiring it. The smaller one is still bomber, although that plastic crap they used to put at the opening for a while has been torn for years. The old big one had a piece of PVC that overlapped the other side of the opening before you pushed the air out and sealed it.
I've been very happy with the Bill's Bags. If I ever need another one, it will be the smaller one. The big one is just TOO big. If I ever got another big one, I'd also get a bunch of long, skinny coated lightweight nylon drybags. I would pack things in the smaller bags and slide them into the Bill's Bag.
A friend has an old purple Seattle Sports bag. I like the color, and if they still made it, I might get one.
I'm still not decided on the new design of the NRS Tuff Sacks. The ones I've had are getting older, so I bought a selection of the new style. The buckle is smaller. Maybe it's just as strong, but I'll have to wait a decade to get back to you on that.
I've never ponied up the cash for a Watershed. That's probably also a good choice if you can afford it.