Factors that affect the decision of which scriber you should use are:
The material you want to scribe
The shape of the workpiece
The amount of scribing you are likely to be doing
Material
Soft materials
If you are scribing soft materials such as wood, laminate or plastic, then a knife blade scriber will make it easier to mark the workpiece and allow you to make deeper score lines for saw blades and other tools to follow.
Metals
Soft metals such as brass, copper, aluminium and mild steel can be marked with hardened steel, tool steel and tungsten carbide tips.
Hardened metals
Metals such as stainless steel, hardened steel and tungsten will require a scriber with a tungsten carbide tip or diamond mounted tip to scribe a line on them as the scriber tip has to be harder than the material it is scribing.
Very hard metals such as tungsten carbide can only be scribed with a diamond mounted tip.
Shape of the workpiece
If you need to scribe a line in a confined space on your workpiece, such as inside a hole or recess, then you should use a scriber with an angled point at one end.
Can you get scribers with different angled tips?
Scribers can have a variety of angled tips, the most common being 90 and 45degrees, and are used for marking the underside of lips, and in holes or recesses.
Scribers with hooked tips are also available for the extremely hard-to-access areas of a workpiece.
Amount of scribing
If you are only going to be doing a small amount of scribing on soft materials, then a hardened or tool steel tip would be the cheapest option and the easiest to sharpen.
If you are doing a larger quantity of scribing or are scribing harder materials such as stainless or hardened steel, then a tungsten carbide tip would be best, as it is cheaper than a diamond mounted steel tip and can be sharpened when needed.
A tungsten carbide tip will stay sharper for longer than a hardened or tool steel tip as well, meaning you have to spend less time sharpening it.
Also, if you are doing a large quantity of scribing then it is worth getting a scriber with replaceable tips. This will allow you to quickly replace the tip when it is worn and complete all of your scribing, then sharpen the tips at a more convenient time.