so far , from what I read online , the differences between the VS city and the "new" VS city are
- new is tri-sync . old is 15/24
- new is jamma/jvs . old is jamma
is this correct ?
Correct. More specifically, the NVC uses the ms2930 manual trisync chassis (this appears to be stock). The PSU used is the NVS-4000 in the NVS (which used a model 3 based amp internally for stereo) and the harness used is the Sega 002 loom. So, no -5V but you can run a naomi cart setup, you would need the sun-psu for netdimm/gd-rom use. Another thing to note, you cannot use the capcom i/o for converting the controls for JVS/jamma. You have to use the sega one where 5-buttons come from the jamma and button 6 comes from the auxillary. So if you want to use one of these for MVS/cps2/cps3/naomi, then the wiring gets a little complicated [just a heads up].
The versus city is NAC based in that it uses the great for 15khz ms9 chassis. I am not sure on the model of the PSU, but I know it has stereo support and I am fairly certain you can use the capcom i/o on the VC. If you only wanted 31khz, then you could replace the chassis with ms2932.
Any other questions in regards to the NVC, then I am certain BIGTIME can elaborate.