Ethernet – the voltage used in ethernet lines (UTP Cables)

metal

Aluminum is less expensive, but will develop cracks if it is flexed too many times. Copper is more expensive, but is more ductile; So it is much more forgiving of being repeatedly flexed.

specifications

The Cat-N specifications determine various limits; Parameters such as:

• how much a signal may be attenuated per unit of distance
• how much cross-talk (signal leaking from one pair to another) is allowed between the pairs
• how much radiation ("leakage" of the signals) is allowed from the cable
• the range of frequencies which the cable's pairs are designed to carry

(and much, much more...)

use cases

There are differences in the insulation which jackets the conductors and the entire cable. For example, "plenum" cable -- meaning it is designed to be used in a plenum, a space within a building which is part of the air handling path for climate control -- is designed to limit how much, and at what temperature, it will emit toxic fumes.

There are options such as full length shielding (grounding) which prevents interference from other sources. (This is not common with Ethernet cables.)

The overall physical diameter of the cable may be a use case limiting factor. If you are install a very large number of cables, that might matter.

Some cables contain a "strain relief" feature; A small nylon string (looks like dental floss) can be added within the cable to help prevent stretching the conductors when cables are pulled into place.

As I recall (and I will admit I am too busy ATM to go research this myself), the RJ standards define the mechanical characteristics of the connector (shape, size, contacts, etc). They do not define the manner of crimping the connector to a cable.

Each manufacturer could make their own decisions on the manner of crimping, but there isn't really much you can vary in this process. The result is that there were two major crimp dies and types of connectors that provided at least the majority (or possibly the entirety) of the market.

This is true prior to Cat6. With Cat6 it is more difficult to adhere to the standard when making terminations, as you have very little room to "untwist" pairs and need to maintain proper separation of the pairs.

This led to a whole new range of connector products and tools that may or may not be compatible with older tools. For instance, I have seen Cat6 connectors where you wire the cable to an "insert" that is then inserted and crimped into the connector.

Morale of the story is that you need to do your research and make sure that you are getting connectors that work with your current tools or buy the right tools with the connectors. On top of that you need to know what you are doing or you may produce cables that will only pass a Cat5 certifications at the extra costs of Cat6.

My advice generally, and especially if you are looking to do Cat6 or better, buy your cables pre-manufactured. The failure rate of hand made cables is much higher and can cost more in troubleshooting/downtime in the long run. Especially since many of these are made in organizations that are "trying to save money" and also don't have the tools to properly test the cables they are making (certification testers are not cheap).