Originally Posted by DonR
I used only the Peco Insulfrog small turnouts on my layout, never
a problem even with my 70 foot passenger cars in
the yards. However, I only used 4 wheel truck locos.
The amount of space you have for your yards is a major
factor in your selection.
I'm going to somewhat disagree with DonR on this one.
First, I rarely disagree with Don, since he's very smart.
Second, knowing how reliable Peco turnouts are, I have no reason to doubt Don's favorable results with the smaller turnouts.
Where I differ is in yard design. I believe in very conservative, and very simple, "yard ladders." (the string of turnouts at the entrance/exit of a yard) Since strings of cars are routinely pushed backward in a yard, I think that's where we want to have the easiest path possible, to every track, to minimise the odds of a derailment.
"Easiest", in this case means larger frog number turnouts. (medium instead of small) and a simple yard ladder arrangement where a backing train only has to make one turn, to reach any track in the yard.
The length of yard tracks can be increased, a little, by shortening the yard ladder. This can be done by using "compound ladder" arrangements, or strings of turnouts that make a train veer first one way. and then the other, in virtual "reverse curves. I don't favor this approach.
Where I needed a shorter yard ladder, I built one with one turnout overlapping another. (I build my own turnouts anyway, so for me, this was no big deal.) If you prefer to buy, rather than build, Micro Engineering sells a commercial compact ladder in HO-scale. Their ladder uses #5 turnouts which would fall between "small" and "medium" in Peco's terms. Micro engineering turnouts are a very close second to Peco in overall quality so if the length of your yard ladder is an issue on your layout, then the M/E compact yard ladder may be something to look at.
Keeping things as simple as possible, along with the previous advice to "go big" whenever you can, will ultimately pay off in reliable operation.