It seems we're starting with a false dichotomy. Each of your knives is both stainless and high carbon. Let me explain.
Stainless steel, has at least 13% chromium, by international standard. The chromium helps prevent corrosion of all types. However, there are all sorts of desirable characteristics for knife alloys, and chromium gets in the way of a lot of them. Manufacturers use very complex formulations, including other elements, compounds and techniques to work around that.
By convention, "carbon" steels have less than around 3% chromium. I say around, because only the term "stainless" has an actually quantifiable meaning when it comes to... well... stainlessness.
The steels in between 3% and 13% chromium are referred to as "stain resistant," "rust free," rust-resistant," "semi-stainless," "stain free," etc. Some manufacturers use the terms in a way in which they could be differentiated, while others seem willy nilly. As far as I know there aren't any real standards governing the use for the in-between terms. Caveat emptor.
All steel is an alloy of iron and carbon. The carbon allows the iron to hardened to useful levels. Any steel, stainless or not, with a carbon content of at least 0.5% is "high carbon." The distinctions between 0.5% and say 0.45% can be pretty subtle. Anything below 0.45% is best avoided.
By and large, most good carbon knife alloy steels have better edge characteristics than stainless. They also feel better on the stones. The can be made harder than most stainless, absent exotic techniques like metallurgical powders. They don't actually require much more care than stainless, but they do require it more or less constantly and right away.
Until fairly recently, carbon alloys could be made with better balances of toughness and strength than stainless. Strong, hard stainless tended to be very chippy. Tough stainless was either very difficult to sharpen or was so soft that edges would collapse at the slightest provocation -- "German" steel for instance.
Some really excellent stainless and stain resistant knife steels have come on the market fairly recently. VG-10 is one of them. VG-10 can be hardened up to 60RCH or so, and has most of the desirable edge characteristics in spades. Perhaps it's greatest weakness is that it can develop very tenacious burrs during sharpening which can be problmatic for most home sharpeners. Nevertheless, VG-10 is one of the best, all-around, stainless steels available.
The ideas of a serious interest in knives, and poor maintenance don't really go together for me -- but that's me.
The typical homecook isn't terribly interested in knives anyway. If you can convince one to keep his knives sharp -- you've gone an awful long way. Even professionals usually work dull, and most of them apparently feel too harried to rinse and wipe. But let's not forget that until 50 years ago, it's all there was, and somehow we managed.
Context is everything, though. Considering what's available now, carbon is more trouble than it's worth for most cooks.
More than three-quarters of my knives are Sabatier carbons of one sort or vintage or another, including all but one of the seven frequent users in my block. They are perfectly suitable for someone with good kitchen workhabits. As it happens, I'm bored with the chef's knives I have and am thinking about buying a new one. One of the knives at the top of my list is made in three models, stainless, carbon and a stain-resistant HSS (high speed tool steel). I'm considering the carbon and the HSS models, but not the stainless.
Neither of your knives are made from one steel. Both are laminated construction of a type known as warikomi or san-mai. Making knives this way allows manufacturers to save a great deal money, and to apply decorative and/or protective layers (jigane) to the cutting core allloy (hagane).
The Tojiro is made from an anonymous metallurgical powder tool steel. Tojiro keeps the specifics secret, but I'm educated guessing either SG-1 or SRS-15. In any case it's either stainless or so "stain resistant" it might as well be, and has a very high in carbon content indeed as knife alloys go -- 1.4% or greater. For what it's worth, cranking the carbon content to achieve greater hardness is the primary reason to go PM (aka metallurgical powder).
The Kasumi's VG-10 is 15% chromium -- so definitely stainless, at around 1% Carbon.
The jiganes for both are stainless as well, but they are low carbon.
While both your Kasumi and Tojiro are decent knives, each has its idiosyncracies. I wouldn't choose either for myself. Nor could I put either near the near the top of their respective peer groups if asked for an independent evaluation. However, that's me. I'd really like to hear what you like about your knives, as you own and use them.
PS. If you want a compare and contrast on the differences between the types of steels Japanese and European knife makers use, and how they impact knife use and performance -- it can be done. But it's a different question.
Edited by boar_d_laze - 8/16/10 at 9:01am