I’m curious as to what are the exact differences
Main differences between IV and V are
- damping trough standard on V, optimal on IV
- Tracking force uncalibrated on IV
- Bearings - later IV's had the same bearings as the V.
- Wiring - copper vs silver
If you already have a IV you would be better off getting it serviced, bearings upgraded to V, and rewire - SME will rewire whatever you like or provide. Tonearms are easily damaged ( which is not always obvious ), so rather than buy a second hand V - better to get the IV serviced and upgraded by SME.
I could not detect anything from the V that stood out as noteable for being an improvement and worthy of aspiring to.
This is subject to opinion and component matching.
When the SME V came out it was a substantial step up from the arms of the day including Alphason, Zeta, Sumiko MDC800 and of course all the Linn arms. Compared to the other arms of that era the sound was cut from one cloth from top to bottom and very organic - the midrange in particular far exceeded the other arms. The SME V does not work on all turntables though - terrible on Linns for example - too heavy. Certainly the build quality is still superior to any of the Origin Live arms.
The SME V is often underrated simply because it is very neutral, self effacing, does not exaggerate any particular parts of the spectrum.
The only poor experience I had was I don't think it matches the Koetsu's very well.