Wel, I gave the Brooks several solid weeks of monopoly. so now I think I'm qualified to compare the Brooks Pure Cadence to the Saucony Kinvara, my former go-to shoe and the one I wore for all my current PRs except the 10k (Mizuno Musha).
I didn't want to switch out of the Kinvara. I love how that shoe fits my foot, and I love the lightweight cushion. But I've noticed a few signs that the way my foot rolls at landing could be contributing to injury. I got the Cadence to add a little support for my pronation-prone right side without changing my strike too much. I have worn stability shoes before, and had terrible knee problems, which were alleviated by switching to a neutral shoe. So I wanted just a touch of stability. Since I've worn and loved the Kinvaras for two years, it would make sense to get a pair of the Saucony Mirage, but I tried this shoe on and did not like the stiffness of the sole at all. It felt nothing like the Kinvara.
The Cadence feels more like the Kinvara in terms of cushion and flexibility, although it seems slightly less squishy to me - probably due in part to the stability part of the shoe! It also has a nice wide toe box, so my wide feet are pretty comfortable, although there are some overlays on the Cadence that rub along my wide bunion area. I tried on the Flows as well as the Cadence, and they fit more closely to the Kinvara and had almost as much mobility - still a little less cushion. But the feel was similar, especially while running.
The heel-toe drop for the Pure line and the Kinvaras are the same: 4mm, so the two feel the same as you land, but the Kinvara offers a wider heel platform. The heel on the Candence is undercut, so you just can't sit around on the heel. It's supposed to encourage forefoot strike but I personally did not notice a difference except when standing; the Cadence almost feels like you're rocking forward. No change when running, though.
I think the Pure line compares well with the Kinvara: similar fit, similar toe box (a little more round in the Cadence, more pointed in the Kinvara), similar weight, similar cushion, similar heel-toe drop.
In contrast, the Pures wear out much faster (I already see compression), allow less mobility on the foot platform due to construction (the "Navband" over the instep), have a slightly firmer landing with slightly better propioception, and in the Cadence, have a smidge more control.
So let's briefly discuss the control aspect: It's minimal in the Cadence, and I suspect it has more to do with the Navband and the cross-over lacing than the medial post. The shoe is really quite a soft shoe, it just isn't as soft as the pillowy Kinvaras, but all that softness does allow some movement of the foot. The Kinvara allows much more because the upper is virtually a mesh sock. I loved that for my bunions (so roomy!), but I didn't love it for my collapsing right arch. The Nav band is just enough to keep my foot in place. Did it do what I wanted it to do? Well, I'm not sure. I have not had as severe medial tibial stress syndrome pain, and my osteitis pubis is very well controlled right now, two things partly attributed to pronation. But I also started a strict stretch and strength routine that is helping, as well, so it's hard to know what is most responsible.
My personal conclusion is that I really like the Pure Cadence, and I will almost certainly buy it again. I think it is a well-designed shoe, and the slight control is just enough to keep me healthy. As far as running experience, the Kinvara's freedom offers a slight edge; I miss the light, cushiony strides. But I have to compromise to stay well, and the Cadence is a compromise I'm very happy with.