SAR cannot be seen as one specific type of operation.
Having had the mixed pleasure of working with these things full time for a couple of years, I believe this cannot be discussed without first putting the operation in context, considerering things such as what you should be able to do and especially the area to be covered - not to mention your budget (but which is perhaps not relevant if we talk about "ideal"?).
The ideal SAR helicopter and your priorities will be quite different for a short range onshore and coastal SAR in VFR conditions than if you e.g. should be able to pick up 25 survivors at 240 nm/10 at 385 nm and return to base in most weather conditions.