Steel is iron with certain impurities added to increase hardness, the most common being carbon. Iron (maybe surprisingly) has a lattice-like crystalline structure when used in knives etc, and the impurities stop the layers sliding over each other so easily in a similar way to putting sand under your tyres if your car is slipping on ice. Well, it's a good analogy, anyway.
Stainless steel (as well as the carbon) has a high content of chrome in it which doesn't, of course, rust, but it's very brittle. There's usually 12-25% chrome content in stainless steel.
On the flat of the blade, this is good: the iron at the surface rusts but then wears away leaving a (very thin) surface layer of just chrome to cover the iron and stop any further rusting. As the side wears, the rust quickly goes, leaving more chrome.
On the cutting edge of the blade, the chrome is a disadvantage because, being so brittle, it breaks off easily and you lose sharpness more quickly.
So cutlery is stainless with a high chrome content because you need it to stay looking good and sharpness is adequate, but you'll notice that Stanley knife blades will rust because sharpness is more important than shininess.
There are more expensive ways to make high-quality stainless steel, but these require more expensive impurities and manufacturing techniques.
Stainless carbon steel is just stainless steel being advertised by companies who hope that people who have been told that carbon steel is best, will think they have got both carbon steel and stainless steel (which they have, but all stainless steel has carbon in it if you are going to get any kind of edge to a blade).
So you have 3 choices:
Stainless: if you don't use the knife much, don't need the sharpest of edges (don't shave, don't need to shave, don't want to shave by holding a knife to their throat etc), don't mind sharpening it more often, and want to be able to leave it in the garage for the winter and it not rust
Carbon steel: if you will use the knife a lot or are prepared to wipe a film of oil on it if you know it will be left unused in a damp environment but want the best, most durable edge, want to impress your friends by shaving with a stupidly sharp knife.
High quality stainless: if you want (almost) the best of both worlds and have enough money not to care that you could have bought 10 or 20 Mora carbon steel knives for the price of the posh one.
As it happens, I've just had to buy a new knife and I decided on this knife (£10)
http://www.survivalschool.co.uk/survival-bushcraft-equipment-107.html
and a Fallkniven DC3 - a diamond/sapphire whetstone (£8.95)
http://www.survivalschool.co.uk/survival-bushcraft-equipment-1617.html
which will give you an unbeatable edge and, with some work, a polished finish to the flats.
The whetstone will sharpen anything, diamond is the hardest known substance, and sapphire the second hardest.
The quality of an inexpensive CS knife from a reliable manufacturer will equal or beat anything else you can get, and it won't rust away if you use it often and grease it up if you are going to leave it somewhere damp for a while.
Ian