I can chip in here, as I’ve got both a Hattori FM VG10 petty and an Ashi (JKI) Ginga Stainless petty (both for my wife).
I’ll try to keep it objective as much as possible, but feel free to ping me questions if this isn’t what you’re after:
Hattori FM VG10 petty
- Really nice western handle shape. My wife prefers this handle over the Ashi.
- Quite thin grind and geometry.
- I have had real trouble learning how to deburr this knife effectively (which is detailed in a whole other thread), but with sufficient technique and a bit more attention and patience it can get just as sharp as any other knife.
- Edge retention is pretty good, slightly more than the Ashi but slightly less than Magnacut etc.
- Fit and finish is okay, but I rounded the square spine and blunted the heel spike to make it a bit more user friendly.
- I’ve only owned one VG10 knife so I don’t have an objective comparison of the heat treatment of this knife relative to others, although I know a number of people here have had issues with poor heat treats on cheap VG10, I can’t say definitively whether mine is or is not affected by the same thing.
Ashi (JKI) Ginga Stainless petty
- Fit and finish is a bit nicer, didn’t have as much to do to the spine.
- Geometry and grind I find a bit thinner and better for our typical use cases.
- Western handle is okay but a bit boxy (reminds me a bit of a Wusthof).
- Slightly easier to sharpen and deburr.
- Good heat treatment and fairly hard at about 61 Rockwell
- Jon from JKI is always lovely to deal with and I enjoy supporting his business.
Of the two, I would always recommend the Ashi Ginga stainless over the Hattori, but that’s based on my personal preferences for easier to sharpen simple stainless, thinner geometry, and good heat treat. That’s not to say I’m unhappy with the Hattori, just a personal preference based, and your mileage may vary.