I guess it depends on your need. Wyes are best for turning locomotives, not trains. Wyes also take a bit less less space. You'll need special wiring on both.
I agree, it depends on several factors. For example, is it really a true #4, and if it is, and it is curved through the entire diverging route, will your rolling stock accept that sharp a radius? How about coupled, and how about backing...while coupled? What is your aim with any kind of turnout in this location? Are you turning entire trains or just wanting to park something? Maybe just turn a couple of locomotives?
I guess I'm confused about the original question. Is it about a #4 wye turnout vs. a #4 left-hand or right-hand turnout? If so I believe a #4 wye would have divergent angles the same as a #8 left-hand or right-hand turnout. That is good but the #4 would have a straight route with no divergent angle on that route whereas bought routes on the wye would be divergent. I think I'd pick the wye if this was to be used to form a reversing section vs. the #4 if that is the only other option. Now saying all of that maybe it isn't even relevant to your question , Sumner
I think that I would agree that the wye would be better for sure in a reverse situation or a spot where you split to two tracks that are not going to be parallel to each other. If it's a case of just going from one main to double track, then the #4 or even better, a #6 would be the way to go.
