Wrong.....
I believe the Herc has a homer system to allow a search for beacons operating on 243, i.e standard UK military system, so eletronic search capabilities of the two aircraft would be similar. The current Herc radar is good enough to find smallish contacts, fishing boats etc, but will undoubtably not be as capable in a maritime environment as a Nimrod's. Herc will have greater endurance than a Nimrod, although, given its slower speed, that does not necessarily mean a greater patrol radius. Herc can fly slower in the search, giving more time for a pair of eyes to scan the same area of sea. Herc can drop a SAR package but probably won't carry the number of dingies a dedicated SAR Nimrod would have available. Nimrod has more extensive maritime comms and a crew compliment to run several intensive radio nets simultaneously. Nimrod has more comfortable positions for carrying out visual seach procedures....
So, the Herc can do a capable electronic/visual search in a SAR incident, especially given a well trained crew. It will be nowhere near as capable as a Nimrod in a large scale, command and control type incident, such as a repeat of the Piper Alpha. However, to write off a Hercs capabilities in SAR as nil is incorrect, as has been demonstrated before in the South Atlantic.