If your of limited Electrical experience, and just want to "Git Er Dun" .. Or space issues..
Then, A one wire is the best way to go..Although it has it's drawbacks..No Direct
provision for Lamp or Amp gauge connections..(unless inductively coupled), But you only have One wire and ground to deal with, and you Can ALWAYS use a Voltmeter.
If you go 3 wire internally regulated, you can direct couple an Idiot lamp and AMP gauge..to integrate it into a stock harness & instrument cluster..It takes a bit more expertise & Time, but nothing earth shattering if you can follow a schematic..and have some basic tools..
A 3 wire External, takes a lot more expertise, because you need to throw a regulator into the mix..and make it all play, but again, If you have some knowledge, you should be able to do it..
They all will perform as advertised, and last about the same, So it really boils down to your personal preference, skill & Tool level possessed.