They both work equally as well on Warmoth necks. It's more of a "do want the red ball or the green ball" kind of question. 9 out of 10 1 11/16" locking nut preps we do are for the R4. R3 works good to bring the strings in a bit if you have binding on your neck and you want to keep the strings off of it. Or perhaps you have had a problem with pulling the strings off the side of a neck when you play, R3 may be a good idea for your playing style then.