Forgive me, but I still struggle to understand the differences. If I want stay alive (prob not necessary on a class 47 but relevant maybe for a 08) I should avoid the 638d. Out of the others, what does a higher power rating and adjustable low voltage output give me in the real world? Any benefit to slow speed running? Is an extra 2 function outputs worth having? In the absence of sound I guess I only need function outputs for light combinations or are there any clever aspects to save a function or two for?
Comments very much appreciated, thanks, Henry