There are many different things to consider when buying bondage cuffs, and today we will discuss the most important ones.

Material:

Leather – leather is a natural material that comes from animals. Cow leather is quite commonly used but others can be used, such as deer. Oftentimes bondage cuffs do not declare what leather the animal is from. Leather is a soft material that is very strong. It is quite difficult to break leather. If you properly take care of leather it can last for years and years. It is also a water resistant material, so some water on it is no issue, but it should never be submerged in water. It is also quite flexible. Sometimes it starts out stiff, but it gets more and more flexible with use. Leather is a porous material so if bodily fluids get on it you can never fully clean it, but in my opinion these are the most comfortable cuffs. Leather also tends to be quite expensive. Patent leather is the same as normal leather, it just has a shiny finish. Leather also requires some maintenance and requires conditioning every so often. Leather cuffs are in my opinion good if you know you will use them often and want a high quality item.

Rubber—This is a material most people are familiar with. This is the same type of substance you find in your tires and certain sex toys. Rubber is also very resilient to damage and can last a long time. It is waterproof and you could get your cuffs as wet as you want without any issues. It is quite flexible and easy to bend around your wrist. Rubber is often used for its aesthetic appeal and does tend to be a bit tacky and can chafe. Rubber is a porous material so if bodily fluids get on them they can never be fully cleaned. These are best in my opinion if you have a rubber/latex fetish and want your cuffs to fit your aesthetic preference.

Metal- These are very hard cuffs that have absolutely no flex to them. Metal is the most likely to cause damage to your wrists. If you struggle with leather, rubber, or neoprene it moves with you. If you struggle against metal it will dig into your skin and potentially cut it. Metal is non-porous so if you get bodily fluids on them you can sterilize them. Metal also has the most weight so you will feel them the most. Metal also will not break. It is a very strong material and can likely last a lifetime. Metal also has a very industrial aesthetic that some people like.

Neoprene—This is also a man-made material. It is very physically tough and can take a lot of abuse. It, too, is very flexible and will conform to your body. It has a closed cell structure so it is very easy to clean. It might retain bodily fluids so you should be cautious if fluids get on it. You can completely submerge this material in water with no issues. This material tends to be quite inexpensive, so it is a good starting material to determine if you like bondage equipment. Neoprene is a tiny bit tacky. In my opinion leather is more comfortable, but it is also more expensive.

Lining: There are a number of materials that can line the inside of cuffs.

Fur — You can get fur lining in your cuffs, typically faux fur. This adds a softness to the inside of the cuffs and can make them very comfortable. Fur does tend to get damaged quite easily so if you struggle against it a lot it might become damaged. I think fur is good for beginners who are looking for something very soft and less intense.

Leather/Neoprene/Rubber/Metal — The inside of the cuffs can be the same as the outside of the cuffs and they will have the same property as the outside.

Padded—This is typically only for leather cuffs. Sometimes they are padded. This makes them more comfy and cushy. These cuffs are more comfortable, but typically more expensive, take up more room, and weigh a bit more.

Suede — This is also a type of leather. It is very soft and very nice against the skin. It does not do well with moisture, though. Moisture wrecks suede so if you sweat a lot or envision your cuffs ever getting wet this would not be a good choice.

Miscellaneous There are some other considerations to take into account

Locking/Non-Locking – Some cuffs come with a locking buckle. This allows you to place a lock on them and prevent the wearer from removing them without the key

Color — The color of your cuffs can be important. Typically metal is only silver, and leather is normally black, but you can find it in other colors. Most materials do come in a variety of colors, but sometimes you pay more for colors.

Number of attachment points — Most cuffs have a ring for attaching something to it. Some only have one attachment point. Others have three. If you want to tie your cuffs to multiple points you will have to find a cuff with more than one O or D ring.

Dimensions
Width — some cuffs are very thin. These can be good if you want something lighter, want something discreet, or if you like the aesthetic of them. Some cuffs are very wide and very heavy duty. These can be good for someone who wants more constricting and intense bondage.

Thickness — The thickness of the cuffs can change, especially with leather. You can have 1-3 sheets of leather stacked on top of each other. The thicker the cuff the heavier and more constricting it tends to feel.

Length — Cuffs come in different lengths. If you are a female you might have to be careful that the cuffs tighten enough that you cannot slip your wrists out of them. If you are a male you might have to make sure the cuffs will actually fit around your wrist.

Hopefully you now know all of the aspects of bondage cuffs. You can choose the material and characteristics you think is best for you. If you can go and try some on in person I recommend that. It is hard to explain how all of these feel and fit, but if you cannot go somewhere to try on a set, hopefully this guide gives you a good idea.
As always feel free to ask questions in the comments.