My first Kayano 17 impressions over the Nimbus 12:
- slightly more substantial feel
- more heel strike cushion
- more stability
- narrower toe box 'feel' (not actually narrower. I'll explain below)
I purchased and compared Kayano 17 to the Nimbus 12 for use primarily as walking/hiking shoes. Both feel great on my feet, but the Kayano 17's have a slight edge in stability as well as having a bit more heel cushioning - I did a simple heel walk and heel bounce test. Toe padding seems about equal. For this I did toe bounces for 30 seconds with each pair. Overall I'd say I notice the Kayano's on my feet more, whereas the Nimbus feel, well, more nimble, more like a 'pillow' as another review said of the Nimbus. Make no mistake; the Kayano's are super comfortable. Different shoes for different people, essentially. I don't know the actual weight difference between these, but holding them I'd say very little; it's more the perception while wearing them that the Nimbus's are lighter, even though they probably aren't, or aren't by much.
Kayano's toe box 'feel' is a tad narrower than the roomier-feeling Nimbus toe box (both pair are 7.5 men's; medium "D" width); so the Nimbus's allow my toes to expand when striking first with my toes (hiking steep uphills, running up steps, etc.). I think this has to do with the Nimbus meshing; it's lighter and stretchier, which may give the Nimbus a slight advantage during hot summer months when feet tend to swell, or for people with wider feet that aren't quite wide enough to justify going to the next width size up. Too much room risks blistering and/or less stability; too little crams the toes together.
Speaking of stability, both seem to include the same ASICS technologies, but the Kayano's fare a bit better here. I tested this simply by holding the heel part and the widest part of the shoe and gently trying to twist it. Wearing them also seems to give the nod to the Kayano's. Venturing a guess, reasons might include a slightly beefier last, higher heel shank and different lace patterns; whereas Nimbus laces follow a slight curve from tongue to toe, Kayano's use the more traditional straight-line lace pattern.
Both shoes have nice heel-to-toe roll. Some sneakers, even those built on a curved last, inevitably give that 'slap' when the toe strikes. Both these shoes employ curved lasts. I compared the lasts by visual inspection and by rolling opposite sneaks bottom to bottom. Visually speaking, their shape (width/length/curve) appear nearly identical; only the tread looks different. the Kayano heel shank is noticeably higher which as I said probably contributes to stability. Of course, I can't speak for how their internals are constructed.
I value feet health since I *love to walk and want the best for all my joints above my feet, so the $50 difference (depending on which color/size you get) between these shoes counts towards 'healthy foot insurance.' Since I'll use these as my everyday shoes, and for for walking two miles in the forest a few times each week, I'll probably replace them within a year; even the most expensive sneaker becomes a liability as they begin to deform and flatten over time.
Yes, the Nimbus 12 is really a great choice (and cheaper), but for the reasons above, the Kayano 17 running shoe is my choice.
Happy shopping :)