Both links are from the same thread, sorry!!!
HALion 4 comes with the HS content plus a bit. Whether it’s worth going to H4 is a subjective opinion, but ask yourself whether the extra sounds that comes with H4 and the detailed editing capabilities is worth the extra money or not. To me, it is absolutely worth it, because I need the more in-depth editing. (And extra sounds is always nice!) 
Here is an unofficial info breakdown based on available info at the time:
Official: