These are two of my favorite chef knives, but for very different reasons. While both ultra-modern in design, that's one of the few similarities they share. They're both fantastic chef's knives for different reasons, and I'd happily recommend either one, depending on the task at hand.
Though both these knives get my highest recommendation, it's in different contexts.
The Ken Onion knives are innovative designs, very different from any traditional kitchen knife. They are extremely ergonomic and perfectly suited to cutting, chopping and slicing. It's high-carbon core and edge give it a wicked edge, but the layers of Damascus steel give it flexibility and stain-resistance. It's an aesthetically stunning knife.
It's an unusual design, however, so it may not be the best if the chef isn't willing to get used to the design. They are also significantly more expensive for what's ultimately a designer knife, so they may not be well suited to a busy professional kitchen where someone may grab your knife off the line and abuse it.
The Global line of knives, on the other hand, is a study in modern minimalism. By all appearances, forged from a single block of high-vanadium and -molybdenum steel, it's hollow handle makes it extremely lightweight. It's a more Japanese design, trading the heavy bolster and finger guard for an easy elegance. For a top quality knife, the Global knives are extremely reasonably priced.
On the other side of the coin, this knife's steel may not give it the hardness or sharpness of high-carbon or high-carbon stainless steel. The molybdenum enhances its hardness, and the vanadium improves its grain (for sharpness), but it will need some very regular honing to keep up with better steels, and may never have as sharp an edge as high-carbon counterparts.
Both the Shun Ken Onion knife and the Global knife are designed in the Japanese tradition. They don't have a heavy bolster or finger guard extending to the heel of the blade. This is where the similarities end, though. The Global G-2 has a typically tapered blade shape, with a gradually sloping belly up to the tip. The Shun Ken Onion knife has a more exaggerated roll in the belly as it approaches the tip, a design meant to make chopping an easier and safer task.
The Global knives have a more typical handle shape suited to a variety of different grips depending on personal preference. It's small enough that it's comfortable even for cooks with smaller hands, and its lightness makes it easy to use. The Ken Onion handle and bolster, however, is designed to work only with the pinch grip - the preferred method of holding a knife by most chefs - but isn't well suited to other ways of holding the knife.
The Global knives also have a very robust handle, it being all one continuous piece of steel. The Ken Onion has a composite handle made up of a full tang extending from the core of the knife and a synthetic handle covering held in place by rivets.
The Shun Ken Onion knives are all composite blades made up of more than one kind of steel. A high-carbon steel core extends all the way down to the down to the edge, leading to excellent sharpness and edge retention. The core is then sandwiched between 16 layers of rippled Damascus steel, a softer stainless steel that protects the brittle core from breakage and stains. The textured surface also traps air, preventing food from sticking to the blade.
Global uses high-molybdenum and -vanadium stainless steel for its knives. The steel is hardened by the molybdenum and the sharpness improved by the vanadium, but it still doesn't hold up quite as well against high-carbon or high-carbon stainless steel.
The Global is clearly the better buy. At less than half the price of the Shun Ken Onion, it's excellent value for a premium chef's knife. The Ken Onion knives demand a premium for their aesthetics and complex design, and are certainly worth the price, but they may not suit everyone's budget.
It's a toss up which of these knives I like better. The Global is elegant, simple, and much cheaper. The Shun Ken Onion is gorgeous, ultra-high performance, but comes at a premium. So here are my recommendations:
Global G-2 Chef Knife is best for the professional in a busy kitchen, the discerning home gourmet with a budget in mind, or someone looking for a light-weight, utilitarian knife to add to their kitchen.
Shun Ken Onion Chef Knife is best for very particular chefs who need the highest performance available, either in a professional kitchen or at home. Likewise, the aesthetic appeal of this knife makes it as much a decorative accessory as a kitchen utensil, so for those for whom cost isn't an issue, it makes the perfect addition to the kitchen.