One wire is easy to fit to a new wiring harness. If you already have 3 wires why would you change what works?
One wire's main drawback is that it is a one size fits all solution to a very minor problem ie. can I be bothered with 3 wires?
The main advantage of 3 wires IMHO is that you can put the Sense wire at a point where you want to get the 13.5V, and you can move it when you modify the rig.
However I lean on the opinion of years of cheap minded accountants at motor divisions worldwide, they did not cut the 50c because there was a reason to have 3 wires.
BagusJeep lives in Bali.
1981 CJ7 258ci - Bagusjeep
1984 CJ7 258ci - Puthijeep
1981 J20 258ci - Gladys
1951 Willys CJ3A/MB/M38 - Little Willy
1995 Cherokee 4.0 - CHEROKEE