The intended application in this case is some fiddle yards. These fiddle yards are intended for use in an automated layout. The part of the fiddle yards in question will be dealing only with light engines. These will be steam engines - anything from a Lord Nelson to a P class.
Here is the relevant part of the fiddle yards using the short Y:

And here is the equivalent part using the three way:

The short Y has a radius of circa 610mm. The minimum radius curve on the layout is 600mm. The three way has a minimum radius of 980mm - the same as the medium radius turnouts. On minimum radius alone, the three way is preferable - but I have heard of this being unreliable in the sense of prompting more derailments than its simpler counterparts. Does anyone have experience of this such as might be able to advise which may be preferable in this situation?