I do tech support and the argument of TIA-568A vs TIA-568B vs 'whatever, but straight through" comes up every now and again. You should use the appropriate standard for your application.
Since you're referring to Ethernet, you should use Cat5e or Cat6 cable and terminate with the TIA-568B pinout.
TIA-568A
This standard is acceptable/meant for voice communications. By voice, I mean telephony. You would probably see this on a CAT3 cable, and telecom engineers and electricians are probably familiar with it. Any analog voice systems would probably be using this standard, even if they were using a higher CAT cable like CAT5.
This pinout should not be used for data networks, though it will function to some degree; you may see errors, reduced data rate, or other less-than-desirable results.
TIA-568B
This standard should be used for data networks, packetized video, or other intensive applications (throughput or bandwidth).
I don't think there is a negative consequence to using this standard for voice, but it goes against convention, so I would not use this standard for voice communications.
Random straight through
Sometimes, someone will tell you that as long as the ends match, you don't even need a standard. That may suffice for electrical conductivity, for example if you are using some CAT cable to control a relay, but for communications (tele- or data-), you should use the appropriate, relevant, standard.
Misc notes
- The actual wires in CAT cables have different lengths and twists per turn (see Wikipedia), so the choice in pinout does matter and has real world consequences.
- 10/100 mbit Ethernet uses 2 of the 4 pairs, while 1000 mbit Ethernet (Gigabit) does use all 4 pairs of the CAT cable.
- Wikipedia may say that -A or -B is fine, but from real world experience, use -B for data networks.
- Telecom engineers, electricians, or other analog-based technicians will probably give you the most static about how the pinout doesn't matter or that "it's all the same anyways". In such a case, they do not understand the complexities of the data communications world. They may not be wrong for the tech they are used to, but data communications are different than what they are used to working with.
- TIS-568 Standards
- CAT5 Cable