Since they use the same new Goretex Active Shakedry material I was curious and bought all three to compare. Here's a short comparison:
Gore One GTX: Fit and construction are sloppy compared to the other two. Cuffs are loose and zipper feels cheap among other issues.
Castelli Idro: Pretty well made in terms of construction. Fit is decent with one glaring exception. The shoulders and area around the arm pits are way too tight. I'm 5'11, 160lbs, not a big guy at all. This was with a large. Also tried on the XL and it was too big as expected. Considering this material still only comes in black, I liked that Castelli put some color into the jacket with the red zipper and other laminated red detailing. I'm sure it added a few grams, but worth it imo. The elastic at the hem is a nice design but a bit tight even on my relatively thin body.
7mesh Oro: This one takes it by a mile. The fit is absolutely superb, I can't underscore this enough. Jacket just disappears on your body when you are riding. At the same times there is no wasted material. With the other two you can see some areas where material is bunching up or hanging off you when on the bike. With the 7mesh everything just hugs you without feeling constricting at all. It's really quite something. Construction is also a step ahead. The stitches are tighter, the seam tape is smaller. Everything is just better put together. Minor thing I don't like: zipper is waterproof unlike the other two which also means it's stiffer going up and down.
It was an easy decision to keep the 7mesh and return the other two. About the Gore material that's in all these jackets: I used the 7mesh for the first time over weekend. It was damp but much warmer than I thought, and I was way overdressed underneath. When I got home I was almost completely dry underneath even though the jacket was zipped up the entire time. I could barely feel some dampness in the baselayer. This new Gore material is the real deal in terms of waterproof breathability. Chicago isn't exactly a rainy area, but it is windy. To date this is the most breathable windproof material I've used. Also a shout out for the Arcteryx Phase baselayers, performance and comfort way better than any of the cycling specific ones I've had.
I'm a regular paying customer that's very picky about my gear. No sponsors or comps. I've looked at various pieces from Gore, Castelli, Rapha and 7mesh over the last year. 7mesh is a few steps ahead of everyone else in fit and construction. You can see the detail poured into their stuff, the patterns and section cuts in various sections are quite unique. Castelli is well made but not at the same level, fit is good but not definitely not at the same level and can be hit or miss. I like some of the Polartec materials Rapha uses but the fit is really not great at all imo and construction is also not quite as clean. Gore should stick to producing great materials, apparel is not their strong suit. I still get on best with Pearl Izumi bibs. Generally speaking I think cycling apparel standards have been taken to a new level with 7mesh. Finally cycling has the same quality gear the outdoor sports industry has enjoyed for so long with Arcteryx.
Left 7mesh Oro, Right Castelli Idro, Bottom Gore One