Better is pretty subjective. ERR Railsounds come with a Baby Fatboy (40mm diameter). K-Line comes with a flat 50mm speaker. Non baby Fatboys are 50 mm but I am not sure if the greater height will fit.
The surprising thing to me about scale K-Line engines is the volume. Even with their RS4 boards they are loud. I hit a Aux4 a few times to lower the volume.
With ERR RS and baby Fatboys I am looking to crank the volume up beyond max.
I would suggest trying ERR to determine for yourself if its better. You can always use it in another engine if it doesn't meet your expectations.
Pete
