'Hello, my name is XXXX and I'm a model railroader"

I went along to the local NZR modelers group ( I think it was the S scale NZR modelers group, but I appear to have buggered that up now). Different format to what I'm use to. first a sit around with what everyone has been up to. I took the Da along, and surprised a few by producing it out of my coat pocket. So other nice models were displayed.

After this support group, we headed off downstairs to 'Der Room'.
The guy was an excellent modeler. a beautiful collection of wagons and loco's, hand laid track which was just gorgeous (despite not having track chairs), and with some fantastically well made buildings as well). I'll point out here that I do not give praise lightly.
'Can we see something run?'
'Sorry, but I've got to do a bit of work on the locos to get them going well.'

The collection included a north yard A that had been modified by Kevin Barry, a Berntsen Ab (which just looked wrong), a JG models Ab, and a Ja that looked like an early John Gardner model. And none of them went right. the conversation continued, with several members of the group relating their trials and tribulations with assembling S scale loco kits. most were returned to the manufacturer for a rebuild. One in particular was praised for his chassis skills, but not for his superstructures.

I guess its a problem that we have avoided in NZ120, as no one in their right mind (if you are not, please don't be offended) would build a mechanism, and we have got by using close enough stuff from N scale.
My attempts to make N scale steam locos closer to the prototypes that they represent have ended in disaster.
So, throwing this out to the peanut galley. What would you prefer; prototype fidelity, or something that looks OK, but will put in the hard yards on the layout?