I havent tried a newer Silvia so take these comments acccordingly.
IIRC the changes in latest silvia [2007/2008-ish] are mainly cosmetic: Different style drip tray and Chromed plastic group surround.
I have also read that the brew thermostat was changed from 110C to 100C but have not confirmed this for myself [could also be US models only or something like that]
If this is the case, I dont imagine it would cause significant changes in the cup on the proviso you would pull the shot at a different point in the cycle.
I thought that the combined boiler+heating element changes were made in an earlier incarnation to the latest model.
In mine [2004/5] they are seperatable, so the change would lie somewhere between that and the latest model.
Therefore, the advantage you mention is somewhat offset by having to source and buy a relatively used machine [>2+ years] and of course, unless it comes from a fellow snobber you wont really know/trust its history.
If you use the machine properly: ie prime the boiler following steaming, dont leave it on in steam cycle for long periods of time, tighten the steamvalve at the beginning of each session and descale in accordance with your water quality ...... you should NEVER have element issues.
If $$$ are not your main driver, then the most significant advantage is the support + backup gained by purchasing a new machine from a reputable dealer [ie site sponsor] .