I use both high carbon steel and stainless steel along with natural and synthetic handle materials in the construction of my knives. Each component has its advantages and disadvantages. Keep your knife clean and dry, oil it occasionally (I prefer mineral oil since it is cheap and food safe!) and never put it in the dishwasher. If your knife comes with a leather sheath, avoid storing it in the sheath for long periods of time, as leather can absorb moisture and cause your knife to rust.
High Carbon Steel
High carbon steels are the time-tested recipe of knife steels - knives have been made out of them since Medieval times. Different formulations exist to maximize different attributes - hardness, toughness, edge retention, etc. but the common theme is that they have a high carbon content but are prone to rusting. Treat your high carbon steel knife like you would a cast iron pan: use it often, keep it clean and dry, and oil it every now and then and it will outlast you. High carbon steels will develop a patina with use, and like a cast iron pan's seasoning, it will help protect the steel from corrosion. Acidic foods like lemons, tomatoes, and other fruits and vegetables will quickly promote oxidation of the steel, which will result in the patina. A common finish I apply to high carbon steel blades is stonewashing - forcing a dark, almost black, oxidation of the steel using ferric chloride acid and then stone tumbling the blade for a beautiful finish that helps resist further oxidation.
I use several different kinds of high carbon steels, each with their own pros and cons. Originally designed for bearings, 52100 is a steel I'm using more and more due to its superior edge-holding capabilities. It can be heat treated to attain high hardness and works well for most knives. The tradeoff is that it is slightly less tough than some other steels. 80CrV2 is the king of practical toughness, making it well suited for field use and larger outdoor knives. I also utilize O1 Tool Steel, a time-tested tool steel designed for cutting tools, drill bits, and other industrial applications. It is a great all-around steel balancing edge retention and toughness. I use it mainly in my high carbon slipjoints. To a lesser extent, I will use steels like 1095, 1084, 15N20, and 8670, all fantastic steels in their own right, but we all have our favorites!
Stainless Steel
Stainless steel has been around since the late 1800s, and different formulations have been evolving ever since. From the humble 440 series to new steels developed specifically for high performance cutlery like Magnacut, there are plenty of stainless steels to choose from. Due to a high chromium content, they resist (but are not immune to) rusting and staining from oxidation. You should still keep your knife clean and oiled if you have a stainless knife, but it can handle more corrosive conditions without rusting. Stainless steels take a more controlled environment to heat treat and often benefit from cryogenic processing to get the most out of the steel's characteristics.
For my stainless knives, I often use AEB-L and Nitro-V, both cutlery steels that perform almost identically. AEB-L was originally designed for razor blades, so that should speak to its performance! Nitro-V takes the best characteristics of AEB-L and adds some extra Nitrogen and Vanadium to elevate the corrosion resistance. Both are excellent options for the field or kitchen. 154-CM is a classic stainless steel that balances toughness and edge retention. It is a time-tested steel that has a solid reputation for an all around great steel from the field to the kitchen. As I expand my portfolio, I will be branching out into other "super steels" which are developed using powder metallurgy to make ultra-refined and consistent high performing steels like CPM Magnacut, S30-V, S35-VN, S45VN, and many others. Stay tuned!
Handle Materials
The knife's handle is the connection from the user to the edge and has to perform every bit as well as the knife steel. I use many materials from natural materials like wood, antler, and bone to modern synthetics like G10, micarta, and resin composites. Natural materials tend to require more maintenance but offer a classic look and time-honored performance. Modern materials like micarta (phenolic-resin impregnated fabric) and G10 (resin impregnated glass fiber) resist water damage/swelling, UV degradation, and can come in many different colors and patterns.
For my slipjoint folding knives, the knife's structure is made up of a liner, bolsters or pivot, and pins, all of which are usually made up of a metal. Stainless steel, brass, nickel silver, or copper are all materials I use for these purposes depending on the knife's design and purpose.
In the end, the choice is up to you! For best performance, keep the whole knife clean, dry, and well oiled and it will work as hard as you do.