The three knives you mentioned, and the three more I'm adding are all wonderful. If you really want one more than another for even the silliest reason it's still a choice you'll be happy with for a long time.
Enough with the forest, enough even with the trees. Let's talk about the leaves.
Masamoto VG:
Like nearly all Masamotos the VG is an all around great knife. Great handle (ergonomically), great geometry, great edge characteristics -- you name it. The outstanding characteristic though isn't any particular characteristic but the overall rightness of the knife. Masamotos are a lot like good Sabatier carbons in that way.
Fairly tall, but excellent agility nevertheless. Easy to keep square to the board.
Perhaps a bit "blah" looking.
VG does not stand for VG-10. The knife is probably VG-5, if that makes a difference to you.
Over the last couple of years, Masamoto has had some issues with poorly fitted handles on their western handled knives. If you decide on a Masa you want to communicate with the dealer and tell him politely you expect him to select a knife with a properly fitting handle. If you put a gun to my head and asked about any other criticism of the Masamoto VG, it's a little on the whippy side.
If I were buying a stainless, western-handled knife for myself, the VG would be one of two I'd consider. The other would be an Ikkanshi Tadatsuna.
Grand Cheff:
I'm not sure that I have much to add to what I've already said. It's a very good, well finished Japanese chef's knife with good geometry and a comfortable handle. A lot of bang for the buck. The outstanding characteristic is how easy it is to sharpen to extreme sharpness. But since you're not going to be doing your own sharpening that's not such a huge advantage. Holds the edge fairly well.
Hiromoto G3:
Hiromoto's claim to fame with their western-handled Tenmi Jyuraku series (G3 and AS) is the high quality of the blade alloy and thin geometry at a relatively reasonable price. The handles are narrow; and if you use a tight grip that could be a problem.
Hiros aren't exactly polarizing, people tend to either love them or like them. I'm a liker. In terms of geometry and overall ergonomics they're good but nothing special.
I actually bought 4 Hiro AS a couple of years ago. We tried them for a few months but moved them on because we didn't like them as much as my old carbon Sabatiers.
Ikkanshi Tadatsuna:
You didn't ask, but you should know. Pricey, or at least comparatively pricey-ish. The same G3 alloy, but a much better kinife than the Hiromoto G3 -- which is a darn good knife in its own right.
Very good handle. Very thin blade for a western handled knife, but not particularly flexible compared to the other knives mentioned except for the MAC. Best edge taking and holding characteristics of any knife in the class.
Fantastic F&F. Everything fit, and the spine and back were beautifully arched.
Another great all arounder, without quite matching the feel of the Masamoto. The overall equal of the MAC. What the MAC gains with its handle the Tadatsuna matches with its slightly better overall geometry, edge characteristics, F&F and good looks.
Duckfat, a CT poster with a lot of knife knowledge, just bought a bunch of them and he's very enthusiastic -- more like rapturous. Tadatsuna wa-gyuto are a dime a dozen around here, but yo-gyuto (western handled) are much harder to find. It took me a lot of time to find someone who'd let me use and sharpen his western handled Tadatsuna, but I finally did it. As you can gather I was impressed.
I would definitely consider this knife for myself in carbon.
MAC Pro:
You didn't ask about this either, but it should be on your short list. Best handle in the business, better than the UX-10 and the Masamoto. I've never heard from anyone who didn't love it.
All around good knife, better than the Hiromotos IMO. Perhaps not the same sense of perfection as a Masamoto but a good deal stiffer. In fact, very stiff by Japanese made knife standards. Also, very well finished as Japanese knives go. People used to western knives have no trouble adjusting. "Best of both worlds," is a fair characterization.
Excellent support from MAC USA. If there's any problem MAC USA will correct it. At least two dozen people have bought MAC Pros based on my recommendation. Two of them had problems (bad handles), neither bought directly from MAC USA, yet MAC fixed it without question and immediately if not sooner.
I don't care for the silk screened graphics. If you don't either, don't let them bother you. They'll come off in a few months with regular use and washing.
The MAC Pro is an excellent knife with its stock, 50/50 symmetry, 15* flat bevel. But for whatever reason really comes into its own with a 50/50, 15/10 double bevel. At 15/10 it's as good as anything with a western handle.
Togiharu G-1:
Another fine exemplar of the class.
Very slightly less good (at least overall) version of the Masamoto VG. The geometry is extremely similar. The handle is POM (which I actually prefer to wood), but is a little narrower and shorger than the Masa's. I can't put my finger on why I don't think the Tog handles as well as the Masa. Less money though.
The brand name belongs to an international dealer Korin. If the knife is sold under a different name by someone else, I'm not aware of it.
The G-1 actually seems to be VG-10; at least according to Korin. But as a practical matter, I don't think VG-10 is any better than VG-5.
It's knife hobbyist dogma that the G-1 and VG are made by the same OEM manufacturer. That doesn't make it true, just sayin' is all.
JCK:
Excellent e-tailer. The owners, Koki (speaks, reads and writes English) and Jemmi (his Dad) are fantastic.
I've bought about half a dozen knives from JCK over the past four or five years and never had any problems. On the contrary in fact. Things came quicker and went through customs more easily than I would have thought possible.
I'm aware of a couple of issues with poorly made Mizuno Tarenjo knives that were not resolved particularly well -- which involved the same very complicated fact pattern Since you're not buying a Mizuno, it's not sufficiently germane to go into it
Suffice it to say that JCK is great but not perfect, and any purchase you make is almost certain to fall on the great side of the ledger.
Koki gives great service. If you do decide to buy a Masamoto VG through JCK, make sure you tell him you want a really good handle. He'll most likely tell you that it's problematic, but will jump through a lot of hoops to make sure you get a really good one. His own standards are very high especially if you tell him you're relying on him.
Bottom Line:
IMO, the MAC Pro and Masamoto are probably the best knives in this category for you. Neither is particularly "thin," but I don't think you care much about that as both stay sharp for a good long time and neither has much propensity to wedge.
I'd throw the Grand Cheff and the Ikkanshi Tadatsuna in there as well. However, you don't do your own sharpening so you'd lose the best part of the Grand Cheff, while the Ikkanshi Tadatsuna might be more than you wanted to spend.
Hope this helps,
BDL